Forgiving Oneself

"How does one attain peace of mind?" asks the Seeker.
"By forgiving oneself", says the Master.
Forgiving oneself? What does it even mean?
Haven't we always heard about forgiving others to attain peace of mind? Then what is this 180 degree turn in perspective?
To speak the truth, we do not see the demons in our own heart. Instead, we go look for them in other people's hearts. We expect others to mirror our thoughts and wishes, and lash at them when they turn out to have their own thoughts and wishes.
So it is within ourselves that we are to look for reconciliation. It is our own demons that we are to forgive and make peace with.
Not others.
Whatever the others do, they have their own reasons for them. In the process, they may sometimes trample on us, but that is a simple coincidence in the vast scheme of events.
We are not to forgive others, for they are mere instruments through which we bring unhappiness to ourselves.
We are to forgive ourselves for projecting our thoughts on to others; for raising in ourselves crooked hopes of reciprocation from others, when we ourselves have nothing to offer to them.
Not being resentful is the way to a peaceful mind.
Not having regrets is a way to a calm heart.