I'm not sure why it makes me sad to see others achieving the dreams I used to have. Let me be clear. These dreams are ones I chose to give up. Dreams that were out-dreamed by other dreams. Ones I fully expect to make me very, very happy.
My first thought was that maybe it had to do with the fact that I haven't yet reached the dreams I've chosen instead. But I don't think this is it; no, there's a sense of nostalgia to this that I think would be there no matter what. I felt as though I got the chance to look at what my life could have been, and I envy your happiness. It makes me wish I wanted what you want. It feels strangely like I dropped part of me instead of redefined me.
Anyway. I'm glad you're happy. And I know I'll be happy too. And that I AM happy.
Go get it.