As I've just seen, I'm not the only one who listens to some songs only when I'm in the right mood.
I'll have to agree with Harmny. Someone To Believe In is a good song but only when one is in the right mood (in love). Tattoo is another one for those deep in the romance department.
May I- I like to play this one when I am nervous, particularly when I'm about to meet family and good friends I have not met for a very long time.
Lazy Mornin'- Almost always gets the skip button unless I am bored or traveling, then I love it.
Protocol- Don't usually like to listen to it, but when I get all choked up about the war in Iraq, this song really hits the spot.
There are more, but these 3 are the first to jump to mind. I'll post any others later.