I want to feel like the things I did made a difference....

I want to feel like the things I did made a difference. That's one of the reasons I spend time [greeting people] on rope lines, because I'm always thinking, 'Maybe this interaction, particularly if I'm meeting kids, will change someone's life.' That's how I think about the work I do [as First Lady]. It's a rare spotlight. I want to make sure I don't waste it.