It’s all a temporary fix
It’s a temporary fix to relieve you of the loneliness, and save you from the string of bad dates you’ve been on, as well as the dry spell of sex—whatever. Usually, you get back with an ex because it seems better than whatever else you had going on in life. But being with someone because that’s less bad than being single isn’t a good reason to be with them at all. You want to be with someone because it’s a good thing for you. Plain and simple.