A great man is hard on himself; a small man is hard on others.
Placing blame for something is a basic human instinct, but this is not productive or helpful in many cases. Sometimes determining blame is important, like a criminal case where someone has stolen something or hurt someone in some way. In other situations placing blame may just cause you to dwell on unpleasant thoughts, and forgiveness is a better step forward once you know who is responsible. This will help you look to the future instead of dwelling on what has happened.