My advice on love matters is always do what your heart is telling you you should do.

For example: My ex-girlfriend(the one of 3+ years) and her new boyfriend broke up recently. She was feeling sad, and the first person she came to was me, because we've always been close in a friendly way as well. Now she's saying she might want to get back together with me in the summer depending on how things are going. I know I'm not 2nd in line to the other guy, I've always been first, just circumstances caused us to breakup before and it was my fault. Anyway, my mind is telling me not to get back together with her because then I'm just letting her get away with replacing me with another guy who ended up being disrespectful to her(which I'm not particularly happy about.) But my heart, it's telling me to welcome her back and act like nothing happened. I love her too much to care about anything else.