In my last long relationship, he always told me he wasn't sure I was "right enough" for him. He kept saying he was pretty sure that there were women out there who might be a better match. I never minded this too much for some reason - maybe because I was older and knew the grass would always be greener and that eventually, he would figure that out. Turns out, he never stopped looking for that someone better and finally left when he thought he found her.