I've been 3 years with a guy and we broke up a couple of days ago.He used to be a very sweet guy but lately he turned into a selfish freak who wants things his way... or no way... I couldn't take it anymore and we broke up even if I love him very much and I can't seem to live without him... what can I do? Is there a chance to turn him again into the man that used to be once, realise his mistakes and come back to me?talking to him does not help... I'm a complete mess, don't know what to do... I want him to come back to me... but changed

You can not. You can not make anybody change or win anybody back. There is no prize and you can not control how another person feels.

JH is right.
The only thing you can do is remember he is not the same person he was and you are in love with the former. The best thing you can do is get on with your life. Get involved with things like hobbies, interests, clubs socializing and meeting new friends. Keep in mind the things you loved about him and look for those things in a guy that is more likely to be like that than a wishful thinking once was.

U have to moved on gal,, u might be was wrong to loved someone, but life must go on,, n u ve to realise that's he s not your distance! leave and try to forget him even its hard than your thought,, but you must do it for your better future,, u can find anothers good guy out there, because there still got plantys of great guys, u can choise the most best for u,, good luck,,