every man is his own worst enemy

Everyone has a tendency to cause complications for oneself or keep oneself from success, as through self-destructive or self-sabotaging behavior. Of course Tommy's sabotaging his wonderful new relationship—every man is his own worst enemy. A: "Doesn't Greg want to graduate? Why is he skipping school so much this semester?" B: "Because every man is his own worst enemy?" Mike is a great guy, but he gets so anxious on dates that he has a hard time even making conversation. Truly, every man is his own worst enemy.