Trying to be friends right after the break up
No matter under what terms you broke up, staying friends with a recent ex is like not breaking up at all. If you are still communicating with each other and even seeing each other, the cold hard fact that it is over just can’t hit you. Consciously, this person is still in your life and they might be for convenience (which isn’t cool). And so, since just moments ago they were a lover, subconsciously you feel they still are. You can’t really grieve an ex until you distance yourself from them. And you can’t really move on until you grieve. Think you and this ex could make good friends? Great. He’ll still platonically be there in a few months. But, if you fear that too much time passing will make some sort of spark go away, then you’re keeping that ex around for a different reason than friendship.