I Am Negative

Oh my God, I can't believe I'm doing things like this. I'm really angry and I say very, very terrible things because I have been holding everything in for years and preached positivity, now it all blew up and I'm calling people tw?ts. But not just out of the blue, if someone says or does something mean to me then I go off on them. And I realize that it's because I hate my life and it's pathetic so I'm projecting my emotions on to others.
How do I stop this cycle of being so toxic?