@kickycan,
One thing that struck me, Kicky, about what you said was that you both expected that YOU would be the one to MAKE HER HAPPY. No such thing. You make your own self happy and can't rely on anyone else to do that for you.
If two people, independently, are happy and healthy, there's a better chance of making it work and last. But for one person to need another person to make them happy - well, that's a tall order and just wrong. I understand your genetic male stuff kicking in, but that's more of a protective, providing sort of thing, I think, rather than making someone happy. How in the world can one person make another one happy??
Think about it. It's got nothing to do with not being man enough - it's a personal responsibility, not one you look outside for.
Sorry to hear you're having a tough time letting go. But go meet someone strong and happy within herself and see how it goes.