Advice in staying positive?

this isn't about periods or pregnancy or anything like that. 
it's about the mental mind, I find myself always angry. and alone. I think I'm bipolar because every time I get mad another person comes out of me. and I hate it. I hate it so much. I don't want to feel like this. 
I want to feel positive. 
can anyone give me advice on how they manage if anyone goes through this? 
it would be much apriciated ..