Belle, that's a toughy. I don't think I can list just one. There is the whole raft of Sondheim songs from 'Being Alive' and 'Not Getting Married Today' and 'A Little Priest' to 'Loving You.' Then there are the songs that fit a theatrical moment such as 'Betrayed' from the Producers.
Oh, Belle there are too many. My head hurts. So, with Tylenol in hand I give you a song that is apt but doesn't come from a musical - 'Unwell' from Matchbox Twenty. It's a good shower song.
'Try not to have a good time...this is supposed to be educational.' - Lucy Van Pelt