When I think of confidence, I think believing in yourself and your capabilities. It is being able to trust yourself, your preparation, and your focus. Trust that what you are doing and what you have done in your preparation (of equipment, training, nutrition, rest, etc.) is the right thing and believe you have done the best at these things. Believing that you have made the right choices and learning from mistakes. It relates to being able to take something positive out of any circumstance or outcome, accepting it and learning from it.
Confidence allows you to stay focused, motivated, intense, and sensible. When you are confident you are not cocky (overconfident) but able to stay positive even on bad days and not let it get you down. You remain self-assured in all situations, such as when there are challenges (steep and icy course, tough competition). You are able to see these situations as another level to accomplish. It is also very important in being able to perform constantly at a high level.