"That is the thing I can always come back to, whether it is about committing to a shot or about getting out first ball," he told The Times in a 2018 interview. "I think it keeps cricket in a really good perspective for me, where it lands in the scheme of life. If you pick up a paper and start from the front, by the time you get to the sports pages you realise getting out for a duck is not the be-all and end-all."
When Buttler won a recall to the Test set-up in 2018, emerging from the rubble left by the disastrous 2017-18 Ashes tour thanks to his stellar run in the IPL, Ed Smith explained his selection by suggesting he would "bring a new flavour" to England's order as a specialist batsman slotting in at No. 7.
"Who could do that job in a way that was unique, in a way that really brought a different dimension to the whole batting order? The panel decided that Jos Buttler fitted that role perfectly," Smith said. "The message to Jos from everyone around the table was to play his way, to play with the confidence and the flair that he's capable of batting with, and the skill and the decision-making."
In other words, Buttler had the licence to 'f*** it'.
Initially, everything clicked. He scored freely in his second game back to make an unbeaten 80 off 101 balls against Pakistan at Headingley, following that with scores of 106 (his maiden Test ton), 69 and 89 in the four-match series against India and scoring fluently in Sri Lanka.
In his first year back, Buttler was averaging 40.78 while scoring with a strike rate of 64.07. Without quite seeming to reach the ceiling his obvious talents hinted at, it was an impressive return for a batsman whose performances had come in relatively low-scoring series, emphasised by the fact no Englishman made more runs in that time.
But since the start of last summer's Ashes series, Buttler's returns have dipped markedly. In his last nine Tests, he averages just 22.17, with his 70 at The Oval his only half-century. In that time, his strike rate has dipped to 50.40.
Analysing his dismissals paints something of a surprising picture, too. According to ESPNcricinfo's ball-by-ball records, he has been out 'defending' four times, 'leaving' twice, and on three further occasions has been dismissed without looking to score: chipping Josh Hazlewood to short cover at Headingley, edging a back-of-a-length ball from Vernon Philander behind at Centurion, and chipping a return catch to Keshav Maharaj at Port Elizabeth.
All told, that means that nine of his 17 dismissals have come without him looking to score. The indication is that rather than falling to reckless, overly-attacking shots, Buttler has found himself torn between aggression and defence.
Consider, for example, his dismissal at Mount Maunganui in the second innings, when he shouldered arms to an off-stump yorker from Neil Wagner, delivered from round the wicket. In a one-day game, there is little doubt that Buttler would have squeezed the ball out towards cover point or look to muscle it through mid-on, but uncertainty over his defensive game resulted in him leaving a straight ball.
Last week's Port Elizabeth Test provided him with the perfect platform. Walking in at 351 for 5 - the highest first-innings total when he has arrived at the crease since his recall - Buttler should have been ideally suited to moving the game on, counterattacking after South Africa had put the squeeze on Ben Stokes' scoring after lunch. Instead, he struggled to adjust to the pace of the wicket, and chipped a return catch to Maharaj playing a nothing shot on 1 from 15 balls. The innings played by Sam Curran (44 off 50 balls) and Mark Wood (42 off 23) coming in lower down the order served to highlight Buttler's struggle.
In isolation, there is an obvious pattern, which points to a player whose runs have dried up. But there is a further problem for Buttler: the lack of clarity he has been given over his role.
Smith's comments regarding his recall made clear that with England's wealth of allrounders, he felt they could afford to create a totally new role, practically unheard of in recent Test history: a specialist No. 7 batsman, given freedom to attack.
But since then, Buttler has moved up and down the order almost constantly; in 17 innings since the start of the Ashes, his batting position has changed ten times. In the last two years, he has been a wicketkeeping No. 6 and No. 7, a specialist batsman everywhere from No. 5 to No. 7 (and even No. 8, accounting for nightwatchmen), and having been vice-captain in the India series two years ago, his place appears to be one of the most vulnerable in the side.
Part of that is down to the fact that England have been, by the admission of most senior figures at the ECB, a side in transition for the last two years. In Antigua last year, Buttler batted at No. 5, with Stokes, Moeen Ali, Ben Foakes and Curran the men in next; this winter, he has regularly been at No. 7 with one allrounder and three bowlers below him.
That means that since the start of the Ashes, he has only been involved in a partnership of ten or more overs on five occasions, and three of those have been with specialist bowlers (Craig Overton, and Jack Leach twice); of the two with batsmen, one was a 13.5-over stand with Jonny Bairstow trying to save the game in the fourth innings at Old Trafford. While that can partly be explained by Buttler's own lack of staying power at the crease, it emphasises the point that he has rarely been afforded the sort of platform he was given at Port Elizabeth last week.
He has also had the gloves thrust upon him again, and while it is tough to draw much from his raw averages with and without them - the samples are too small and over disparate parts of his career - it is worth revisiting a Telegraph interview he gave in 2015 after the first time he was dropped following a tour of the UAE.
"It was a relief to get dropped," he said, "which is sad in a way because you never want to miss a game. But I was not performing and mentally I got to a stage where I was not concentrating and did not want to be there. I was not enjoying walking out there and feeling like I didn't know where the next run was coming from.
"I would also worry that I would miss a nick when keeping because I would be thinking about batting too much. Keeping wicket is the worst place to be when out of form: you can't hide at fine leg where you might touch the ball once every 10 overs. Behind the wicket you are involved every ball."
Similarly, it is worth reflecting on how much last year's schedule took out of him. He went almost straight from the Caribbean tour to the IPL, into the Pakistan white-ball games and then into the World Cup, in which the stress of the final was so great that he later admitted he "didn't know how I'd play cricket again" if England had lost. He used his week off during the Ireland Test to move house, before heading into an Ashes series. For anyone who has watched the documentary The Edge, which laid bare the toxicity that resulted from the win-at-all-cost mentality of the Strauss/Flower dressing room, that run will seem worryingly familiar.
It is easy to view Buttler's apparently mild-mannered, schoolboy charm from afar and assume he does not suffer the same mental strains that other players do. In a newspaper advertorial last summer, he spoke openly about the "incredibly draining lifestyle" involved with playing professional cricket, and revealed that he has taken up meditation and playing the piano, to help him "gain a much healthier perspective".
"When you're batting with the tail, you try to sum up situations and work out how best you can score. You work out your risk management: what is too much risk? What is trying to push the game on?"Jos Buttler on his poor run
Ultimately, the fear with Buttler is that England will fail to get the most out of a batsman who is no longer a promising youngster, but instead a man who should be approaching his peak at 29. There remains a feeling that he could - should, even - be a once-in-a-generation talent; instead, he currently averages 32.29 after 40 Tests.
"I feel like I'm not quite performing to the standards I need to," was Buttler's own verdict earlier in this series. "Since I've come back into Test cricket I've tried to trust my defence for longer periods of time. I've been able to do that on occasions, but [playing my natural game] is certainly something I'm trying to work out.
"Moving forward I've got to play the situation, but I will try to be a bit more positive. When you're batting with the tail, you try to sum up situations and work out how best you can score. You work out your risk management: what is too much risk? What is trying to push the game on? I want to look to be a bit busier and try to look a bit more on the positive side."
Buttler said during the New Zealand series that he was "'trusting my defence," following sessions with Marcus Trescothick, his former Somerset team-mate, "which has been a big part of trying to improve myself as a red-ball player". Much as they were dismissed by the end of his era in charge of the Test side, Trevor Bayliss' ideas regarding being positive in defence, and conviction in movements, seem relevant; they may not have worked as a top-order blueprint, but they seem perfect for a lower-middle order player.
Ahead of the fourth Test against South Africa, it feels like Buttler's time in the five-day side might be starting to run out. England's next assignment is a two-Test series in Sri Lanka, in which the team's management are willing to place emphasis on their short-term needs as much as their long-term goals with World Test Championship points on the line.
Few will need reminding that Foakes - seen by plenty of England fans as a cure-all remedy to their problems - was player of the series on their last visit, and is an impressive player of spin. There is little question as to who is the superior gloveman, a point furthered by Buttler's untidy showing behind the stumps at Port Elizabeth. Even if Buttler is persevered with as first-choice wicketkeeper, then Foakes will surely travel with the squad, and with the middle order finally settled - Joe Root, Stokes and Ollie Pope seem locked in from No. 4-6 - there are few vacancies he could fill.
With a T20 World Cup at the end of the year, in which England will rely on him as a key player, the opportunity to take some time to refresh between the white-ball leg of the South Africa tour and the start of the IPL at the end of March could well be a better option than travelling to Sri Lanka.
The upshot is that Buttler travels to Johannesburg needing runs, and against a team low on confidence and missing its best bowler, he may have few better opportunities. As for the best way to go about it? He could do much worse than to take a look at the top of his bat handle, for a start.
Matt Roller is an assistant editor at ESPNcricinfo. He tweets at @mroller98