My significant other is so pessimistic. Along with some other bad traits  she has it's making me think of breaking up with her.
What else besides your so's pessimism makes you want to break up with her?
Well, really it's just her pessimism about the future that gets me. She only talks negative things about life and I'm tired of hearing her gloomy music in my ear
Having a partner that has a bleak outlook on things is minor in the grand scheme of things, and ending your relationship because of it is a trivial act. Help your partner through her difficult time instead of abandoning her.
Fuck she's depressing, don't even want to be around her.
If you love her maybe you can work to save your relationship. If she seems upset a lot maybe you could suggest that a therapist might be able to help her change the way she thinks about things so she can be a little more happy with her life.