I got rejected the other day. I met with the head of an organization about using Keyboard Confidential to enrich their community, and he saw absolutely no way for them to use it. If you had described that scenario to me six months ago, I would have been terrified. I hate rejection. But after this 'failed' meeting, I surprised even myself—I felt fine.
As an artist, the reality is that people are going to turn you down. They may like your work but have no use for it (as in my case), or they may not see the value at all. First, it helps if you've already heard great feedback about what you do. Before this meeting, I'd had a string of people be really enthusiastic about my concept. If your idea is good, there will be people who get excited about it. Remember their encouragement.
Second, any rejection is useful because it provides information. I know that Keyboard Confidential isn't for everyone, and it was helpful to get feedback on why it wasn't appropriate for that organization. Take note of why people decline your offers and see if there's a pattern you can fix. (That's why the Keyboard Confidential page has changed recently.) But also realize that not everyone will like everything you do, and learn to live with that.
Rejection is a part of any artist's life. It's never a fun experience, but can be extremely beneficial in improving your idea and discovering who your work is for. Treated appropriately, you can have confidence despite rejection. More power to you.