Just because something was meaningful doesn't mean it has to be permanent; loving each other doesn't mean you're right for each other.4. Sex with an ex is familiar and easy, but according to Your Tango Expert and therapist Mary Jo Rapini, "If your reasons [for having sex] are more about soothing your loneliness or feeling like a couple again, the chances are high that this is temporary filler." In the same way that new relationships have a honeymoon stage, many reinvigorated relationships begin on a doomed high.