Often we need to begin our practice of forgiveness by simply becoming more gentle with ourselves. Saint Francis de Sales once wrote: "Be patient with everyone, but above all, with yourself... Do not be disheartened by your imperfections. How are we to be patient in dealing with our neighbor's faults if we are impatient in dealing with our own?"
I've noticed that people who are hard on themselves are often very judgmental about other people. Self-forgiveness is the key to learning to accept and forgive others. Really!