I posted this earlier in the thread on money and happiness, but it's worth thinking about here with a slight modification:
Most of us have at times clicked into a trance like state wherein we stop thinking and start replaying a tape about something we need to believe. We have all done it as well as watched our friends do it.
When does it happen? When people are trying hard to convince themselves that something is true. You can almost hear the click and whirrr sounds as the canned lecture begins and the eye contact stops, for to maintain eye contact would break the trance.
The older you get the better you become at spotting this behavior in others and--more importantly--in yourself. I finally got to the point where I can catch myself within seconds of starting "Oh man, there I go again with my old story about X or Y." Then I stop and smile.
We can identify the myths about ourselves that we cling to by how much we explain them to others and how often we do so. "But I can't help it! I'm like this because of a, b, c, d, e, f, g, and h." The weaker the "fact" the more we need to repeat it to everyone, including ourselves.
I used to have many rationalizations for bad habits and traits, now I have far fewer. Do yourself and your friends a favor and start dropping the tired old stories and excuses about why you can't change for the better.