When I'm down and I'm talking really down I would think that my worst mistake would be being born. I know that sounds bad but I have moments like that. Not as much thank the Lord.
But if I take a serious look at my life, my biggest mistake would definately be walking away from the Lord for all those years. It saddens me to think that He could have helped me through all those times when I was broken and alone, and I didn't let him. I wish I had.
I still have really down times now, today is a particularly bad day actually, but I know God is with me and he loves me even when Ican't love myself.