What is the psychology of a man who keeps the contact information of his married ex-girlfriend but doesn't contact him?

Everyone has nostalgia for the good things of the past, which is normal, especially men. First love is serious, and so is the woman. Therefore, it is understandable to keep the contact information of ex-girlfriends, because there are still some nostalgia and nostalgia. Maybe I didn't contact because I was embarrassed, didn't know what to say, and didn't dare to call, or because I have a girlfriend who loves me very much now. As long as he doesn't contact, don't push him too hard.

Please accept it if you are satisfied?