I used to be in the same type of situation. And as simple as Echooos answer is, that's exactly what it took.
How to deal with negative people? I live around them and they always make me depressed.
Avoid them until you move, but remain positive towards yourself. Go out and participate in activities that you enjoy, this will help balance the draining negativity and build the relationship with yourself for when you live on your own.
If you are talking about family, although getting your own place can be daunting, the freedom is exhilarating. I could put my shoes where I liked, and eat what I wanted without colonal Mustard (my father) standing behind be watching my every move and moaning.