Proverbs 27:2 (NIV)
2 Let someone else praise you, and not your own mouth; an outsider, and not your own lips.

We must do that which is commendable, for which even strangers may praise us. Our light must shine before men, and we must do good works that may be seen, though we must not do them on purpose that they may be seen. Let our own works be such as will praise us, even in the gates, Phil. 4:8. 2. When we have done it we must not commend ourselves, for that is an evidence of pride, folly, and self-love, and a great lessening to a man's reputation. [Matthew Henry Commentary]

"We're an overconfident species," contends New York Times columnist David Brooks. Brooks calls it a "magnification of the self," and he believes this glut of self-esteem is especially rampant in the United States. To back up these claims, Brooks cites an array of statistics, studies, and observations:
When pollsters ask people from around the world to rate themselves on different traits, Americans usually supply the most positive self-ratings.

Although American students do not perform well on global math tests, they are among the world leaders in having self-confidence about their math abilities.

Compared to college students from 30 years ago, today's college students are much more likely to agree with statements such as "I am easy to like."

94 percent of college professors believe they have above-average teaching skills.

70 percent of high school students surveyed claim they have above-average leadership skills, and only 2 percent are below average.

Brooks observes that a few decades ago it would have been unthinkable for a baseball player to celebrate himself in the batter's box after hitting a home run. Today it is routine.

Similarly, pop singers wouldn't have composed songs about their own greatness; now those songs dominate the charts.

The number of high school seniors who believed that they were "a very important person": in the 1950s�12 percent; in the 1990s�80 percent.

According to Brooks, American men are especially susceptible to the perils of overconfidence. Men unintentionally drown twice as often as women (because men have great faith in their swimming ability, especially after drinking).

"In short," Brooks concludes, "there's abundant evidence to suggest that we have shifted a bit from a culture that emphasized self-effacement�I'm not better than anybody else, but nobody is better than me�to a culture that emphasizes self-expansion." [David Brooks, "The Modesty Manifesto," The New York Times (3-21-11)]