Boasting VS Confidence

Today I was informed by my orchestra teacher, Mr. Joel Powell, that he would really like me to play the solo for a piece that we're doing for Indiana State School Music Association (ISSMA) competition. I told him that I would be glad to do it, so I have to learn a whole new part by March 25, a month away.

Now... I'm not complaining. Not at all. But it did make me wonder... Is there a difference between boasting and acting better than everyone else, and having confidence in yourself? Could having confidence in yourself  come off as boasting, especially with someone of low confidence? I do not like people who act stuck up, and I always try to make sure that I am not acting that way, even if I am really excited about something. I do believe it could come off badly to somebody that doesn't enjoy what they do, isn't good at it, or has no idea how much effort really can go into something. 

I have a lot of confidence in myself when I play... Like Mr. Powell says, if you're going to make a mistake you should make it big. So that is what I try to do. I guess it always just comes down to this; be careful what you say, how you say it, and who you say it to.