will it ever be right?

guy meets girl. girl has boyfriend. guy falls for girl. and eventually girl falls for guy. then girl breaks up with boyfriend to be with guy.

does this situation sound familiar? tell me. will it ever be right? what are the chances that the girl will not do it to the guy also? is it doomed from the start? will it be a vicious cycle with no end?

this is the situation i am in right now. i am the guy of course. and i am paranoid as hell. i hope she will be mine forever.