What do you have the hardest time giving?

I have the hardest time giving beyond what I know I can do. It's easy for me to give blood, or spend time listening to a friend's troubles, or say a prayer for someone in need. It's more difficult for me to give something when I'm not positive that I'll be successful at it, or when I know I can't do all that I need to or want to. It breaks my heart when people expect something out of me and I don't live up to their expectations, so much so that I don't like doing things when I'm not certain they'll come out right.