Letting go and having a blast strengthens your position several ways. It surprises them. They have taken your suffering for granted. They assume it. That's the person they're dumping.
Curiosity is compelling.
You get happy and relaxed with this and it hits them like a bucket of cold water that they don't know you quite as well as they thought they did. We're all sexier and more attractive when we're having a blast than when we're depressed. It's far more compelling than making them responsible for our happiness. When they see beyond a shadow of a doubt you're no longer chasing after their affection they can quit running and make their decision based on what they want instead of the chase they're running from. We often take each other for granted.