I think I have made some poor choices but I would never call my choices as "bullying" another. I personally have been bullied before in elementary school when I first moved to the United States from Korea without knowing any English or anything whatsoever when I was 6 years old? It was pretty rough. I made some hard choices in being unkind to another out of selfishness sometimes, because it was something I wanted and worked hard for that another was going to get if I didn't speak up for myself and make a couple poor decisions instead. I cannot say that any of my actions stand out. I really can't think of anything. But I will say that I have made some poor choices and to solve that in the future, I should think more of how my actions would benefit me but how it would ALSO benefit the other person too.
A habit of rumination can be dangerous to your mental health, as it can prolong or intensify depression as well as impair your ability to think and process emotions. It may also cause you to feel isolated and can, in reality, push people away.