Through the course of life, people move in and out of each others' grasp. They forge alliances, break them, move together and then drift apart. Lifelong bonds are most rewarding, but rare. More often, people make temporary associations, built on a coincidence of interests or desires.
In the Sri Lanka team, Kumar Sangakkara and Mahela Jayawardene share an elemental connection. On the field, on tour and in the public imagination, they are inseparable. In both ODI and Test partnership lists, they are the only non-openers in the top five.
But in recent years, they are not the pair who have brought most success for Sri Lanka in ODIs. Not even close. As reflexes, techniques and temperaments change in the twilight of their careers, Sangakkara has come to a confluence with Tillakaratne Dilshan. They are an odd couple, but strangely good together. The nature of their association has been even more surprising than its success.
At 36, Sangakkara has never been a better ODI batsman. Some sportsmen are said to age like a fine red wine, but in cricket, few have lived that maxim out more emphatically than Sangakkara. He has hit more than 1000 runs in each of the past three calendar years, and is more than halfway to that target again in 2014. In the first decade of his career, he managed it only twice.
There are more arrows in his quiver now: lap-scoops to the fine-leg boundary and uppercuts over third man. Since 2013, he dominates attacks, when he used to wear them down. Not many batsmen in the game are in better shape.
A year older, Dilshan seems to be on an inexorable decline. At Lord's, he had four attempts at crashing wide balls through the covers in the Powerplay, and mistimed the stroke each time. That shot was once his most productive. Yet, through a combination of will and wit, he is now the best ODI batsman he has ever been as well. In his last 16 innings, Dilshan has failed to reach thirty only four times. Of the 12 successful innings, he struck at over 90 runs per 100 balls only once.
Sri Lanka's 172-run second-wicket stand on Saturday seemed like a role-reversal to some but, in reality, it is the new order of things: Sangakkara the bold aggressor with Dilshan's steady support in tow. They have made prolific progress this way.
Since 2012, they have hit 2044 runs in each others' company, at an average of 56.77. No other pair has scored more than 1500, and that average is easily the highest among pairs to have hit 1000 together. It is odd to think that while Sangakkara has become an out-and-out matchwinner, Dilshan has become the more consistent batsman. Since 2012, Dilshan has also made 1081 alongside Mahela Jayawardene - the fourth duo on the list.
Like all good partnerships, Dilshan and Sangakkara are counterpoints to the other's weakness. Sangakkara is unsteady early in his innings, poking at the ball with hard hands, but Dilshan is a more effortless starter, regularly finding the square boundary on either side of the pitch. At Lord's, Sangakkara was in visible strife in the Powerplay but Dilshan eased their burden with two scoops for four off James Anderson. Sangakkara would not climb out of his rut until his score was 8 off 26 deliveries.
As the field goes out and Dilshan's scoring dips, Sangakkara moves to even out the run rate, picking gaps powerfully, forcing field changes, then mocking the new arrangements with a spate of calculated strikes. Dilshan had been on 35 before Sangakkara went into double figures, but Sangakkara would reach fifty first, by one ball. They had had a nearly equal share of the first 100 runs of their partnership, but as Sangakkara grew more fluent, he hit 46 of the last 72 runs, and Dilshan only 21.
Beyond the challenges their right-hand/left-hand combination poses for fielding captains, contrasting styles prevents bowlers from finding rhythm in the middle overs. Sangakkara likes to play spin from the crease, but Dilshan charges forward or slides right back. Sangakkara hits to traditional parts of the ground, but Dilshan puts the ball in strange spaces. Alaistair Cook tried all his bowlers and a variety of fields during the partnership, but only the artificial urgency brought on by the batting Powerplay could shake the pair's grip on the innings.
When Dilshan departed for 71 in the 36th over, Sri Lanka were already well-placed to push for 300. Typically, Sangakkara would forge ahead to triple figures. Of his 19 ODI tons, more than 40% have come since 2012. As their careers twist in different directions, he and Dilshan have found sudden room for each other. Pushed to the brink of defeat in the series, their happy meeting of the ways kept Sri Lanka alive for the final game.

Andrew Fidel Fernando is ESPNcricinfo's Sri Lanka correspondent. @andrewffernando