If you don't have feelings for your ex, if you very much think that things can't really be nice between you and your ex, why would you worry obsessively about whether or not they started seeing someone new? This is such an odd fear that a lot of us can probably to some degree relate to, even if we wish we were above that.
Robert and Mary are in an in-and-out relationship with constant breakups and re-get-back-togethers. They don't have…