This is a hard lesson to learn. If you can learn it then your ahead of the game. I actually think that people who are more sensitive and caring feel more quilt and anxiety than others. People that wear their heart on their sleeve.
The beauty of life is, while we cannot undo what is done, we can see it, understand it, learn from it, and change so that every new moment is spent not in regret, guilt, fear, or anger, but in wisdom, understanding, and love.