It is human nature to only remember the good after the loss of someone or something. Especially when your in the honeymoon stage of the relationship, and make no mistake about it, you are. Force yourself to remember why you are no longer together and talk about those things with your partner now before it becomes an issue again.(fingers crossed that it wont) Set clear boundaries and stick to them no matter what. Also discuss those boundaries with him or her. An easy and simple way to figure out your boundaries is to ask yourself this one question: "if they do (fill in the blank) am I truly willing to leave them over it?" if the answer is yes then that is a clear and dry boundary.