Why is it that when I like someone...?

Ok, I dunno if this is just me but it seems that whenever I actually like someone it never goes very far with that person, but then I've got a boatload of other guys who I don't like always asking me out. For once I want to end up with the guy I actually want. Am I supposed to just keep treating him like I don't like him even when I do? I'm not talking about little boys here, these are grown *** men in their late twenties and early thirties.