I want to tell the negative part of myself to go away
Why do you want to get rid of that side of personality?
I've been a shitty person for a very long time and I'm tired of being a jerk to everyone around me
You're doing absolutely right thing by recognizing your negative traits.  Recognizing the problem is the first step toward improving yourself.
Maybe I should have done this earlier to make my life better.
You shouldn't feel regret for not coming to this realization sooner.  It is never too late to make positive changes in one's life, but at the same time, the sooner you make these changes the better.  As long as you are ready to improve, now is the perfect time.