I'm leaving my girlfriend because I can't help her anymore
Why do you not feel that you can help your girlfriend anymore?
Because I will end up abusing her.
If the relationship is full of problems then it might be best to break up instead of giving each other stress all the time. It might just be that you both are truly not compatible with each other and you should not try to fix something that might be unfixable. Both of you are wasting time and effort that can be used to find a better life partner.
Oh shit...okay...
If you feel you have both made effort to fix the relationship but it is not working, you may simply be better off with different people. If your relationship is causing you more stress than happiness than it is probably not worth being in.