You know the answer. People are their own worst enemy. A few examples:
1. The bartender who can't help aggressively intruding on your private conversation;
2. The rude manners that get someone no slack or sympathy from a restaurant server;
3. The insecure who bore you with their clay pillars of self-esteem to the point that you don't want to hear any more about their school, their exercise regimen, their ancestry, or their possessions and investments;
4. The sexually promiscuous who expect to be accorded the honor of a virtuous Roman matron or a biblical Joseph;
5. The patronizing Christian who consistently mimics a Pharisee;
6. The pedant who expects people to want to interact with him;
7. The panhandler who thinks bullying will get him a donation.
There is a good side to all of this (I tend to look for silver linings): flawed characters tend to self-destruct. You just have to wait.
(Fair Use Source for feet of clay image: http://jtcardwell.tumblr.com/post/6159233110/skewed-views-of-leadership)