Okay, so a lot of articles on self-esteem seem like bunk to me, but this one I encountered in O The Oprah Magazine had a lot of information that hit home for me, especially this part:
Why it that some people, the Donald Trumps of the world, seem to believe only the best about themselves, while others—perhaps especially women, perhaps especially young women—seize on the most self-critical thoughts they can come up with? "It turns out there's an area of your brain that's assigned the task of negative thinking," says Louann Brizendine, MD, a neuropsychiatrist at the University of California, San Francisco, and the author of The Female Brain. "It's judgmental. It says 'I'm too fat' or 'I'm too old.' It's a barometer of every social interaction you have. It goes on red alert when the feedback you're getting from other people isn't going well." This worrywart part of the brain is the anterior cingulate cortex. In women, it's actually larger and more influential, as is the brain circuitry for observing emotions in others. "The reason we think females have more emotional sensitivity," says Brizendine, "is that we've been built to be immediately responsive to the needs of a nonverbal infant. That can be both a good thing and a bad thing."
You can read the rest of the article here, or you can pick up the August issue of O.