My coach has a good saying: "Check your ego at the door." Also known as swallow your pride and be humble! Especially in big groups, he especially believes in this saying. You don't want to be "that guy" who runs his mouth about how awesome he is, and then gets dropped or lapped, do you? That would be, um, quite embarrassing!
But sometimes I think letting your ego out is a good thing, especially on race day. But PLEASE DON'T VOCALIZE IT! Keep it to yourself. Trust in your confidence in your own abilities and think that you are 10% better than you really are. That little bit of "mojo" will go far.
But then there is that inner ego that you need to quell during training, especially on easy days. If the goal is to go easy, GO EASY! Think about how much recovery time you will need if you go too hard during a recovery workout? I am a big believer in active recovery. I think taking days off makes you flat, whereas an easy swim or an easy 5K or 45 min bike does wonders in keep you loose and getting the junk out of the legs.
But then let out that ego on hard training days. That hill that you are always scared of tackling? Puff up your chest and think you are all that and ATTACK that hill! Think you can't hit an aggressive split @ the track? Think you are Usain Bolt and hit the gas
Let your ego do the talking. But keep it to yourself :) Happy Training!