It took me around half a year or more to realise the person I was in love with didn't exist anymore and that the person I thought I could rely on let me down during the only time in my life I really needed somebody to be there. I'd have probably got over things much faster but she made things difficult on purpose by insisting we remained friends, coming round to my house uninvited and, finally, telling me she wanted to give things another go (total bull****) just to stop me walking completely out of her life. I learnt the valuble life lesson that the only person you can trust is yourself and that making somebody so intrinsic to your life is just asking for trouble if/when everything turns to ****.
As it happens, I'm now involved with a new girl and couldn't be happier but equally, I now know, that if things did come crashing down I'd be able to deal with it and move on without it feeling like the end of the world. I won't ever let a relationship define me in the same way as I did in the past.