Just read Janet Reid's 5 things about rejections...
http://jetreidliterary.blogspot.com/2004/08/yes-rejection-isnt-fun-but.html
Good advice. Especially...
5. You just have to get over the idea that "it's not right for me" is some sort of comment on the value or quality of your work. It's not. It's only a comment about whether it resonates with me AND whether I can sell it. I pass on really good stuff all the time.
Hmmm. Maybe it isn't my idea.