One of our minister's recent talks deals with shame, guilt, and worry.
http://slc-atlanta.org/2010/08/fearsome-threesome/
Here's the affirmation that went with it:
"A mind focused negatively on my past or future does nothing to help me. Shame and guilt are useless emotions based on past experiences. Worry is useless because it fears something that has not yet happened. I focus on my present thoughts, and I choose only those that uplift me and support me."