Some months ago, a wonderful person just happened and gifted me two songs: one titled Let Her Go by Passenger and another, Gotta Have You by Weepies. At that point of time, i didn't really understand the irony between these two beautiful tracks nor the accidence of a complete stranger turning into something so incredibly close. To be fair, i still don't. But out of habit, i pretend to. For some reason, i wonder how certain things descend into place while others disperse into sky. Just like Ajay Devgan's Vanraj in Hum Dil De Chuke Sanam. He falls in love with Aishwarya Rai's Nandini at the very first sight and even manages to marry her. But her mind is occupied by somebody else. So what does he do now? Since he loves her so much, it's heartbreaking to see her in despair. In a twist, he decides to help her get back to her lover. That way, at least one of them would be happy. Why not her instead of him? So he takes that remarkably noble step and reunites the separated lovers. It was then she realizes the significance of his action and more importantly, his sincerity—being true to oneself more than others. Hence she can't keep herself from running back to him.
Conclusion: He lets her go so she gotta have him.