I just don't know anymore

Why is it so hard to be a parent? I think the girl is lying to me now, probably smoking and there is some kind of attitude going on. So she wants to be trusted, so all we ask is she is in by 10 pm changed her curfew, tomorrow night is a issue she wants to be out on the weekend...work in the morning so I said 11:30 and she wasn't fussy on that idea. She is sixteen. As in most situations there is nothing you can do about teenagers. No discipline, not saying I would do anything to her but she knows there isnt' much we can do. No consequences. She knows if we throw out a ultimatum with her she is going to throw one back. Thing is her dad will take away something she really wants, so what will she do then? Hmmmm quit school, then its no school you have to work and pay rent, won't work...then were are we? I am tired, I don't need this crap.