Most great athletes have confidence and frankly many have ego in their lives, but the very best and most successful athletes manage to put that ego in check during their training and racing. For me ego is about the athletes around you and has very little to do with one's own place in the sport. When our concern as athletes is on those around us, we lose sight of what we are doing and why.
I am lucky to be around some great athletes, both in the pool and on the bike. I am always impressed by their ability to see the world go on around them without being caught up in it. This was shown this weekend by of all people, Lance Armstrong. He has always been a patient racer on the bike, letting others make the moves and reacting when his time was right. However, to let people out ride him and stay smart on the bike during yesterday's 70.3 took an enormous amount of will power. It paid off too and he ran very well and took second in a solid field.
Our own Cameron Dye is another figure that does this so well. In training he does HIS work. Rarely does he get caught up in macho crap and try to run with those faster or out people. Instead, he does his work. His watts, his pace and his effort. He got a lot of pub last year for his head shake and then re-pass of Andrew Yoder (http://vimeo.com/23752505) last year in Nashville, but Cam's success has not been by overreaching on the bike. It is about training precisely and following through on that training in races.
In my opinion, our ego plays the biggest role in over-training and poor race pacing. Wanting to prove to this or that person that they aren't better than us leads to "easy" days in which we cannot recover.
Remember this the next time a little old lady in toe clips come by you on your easy day. Swallowing your pride is difficult, but it is far easier than not reaching your goals because of hubris.