Roller coaster relationships are painful. When you don't know if you should leave or stay, you may go back and forth depending on the emotions you are feeling. To stop the back and forth, evaluate the positives and negatives when you are calm.
The urge or wish for revenge seems to be hard-wired and the decision to get revenge seems to bring pleasure. The results of acting on your urge for revenge are more complicated. Sometimes you may feel better and sometimes you will not.