Forgiveness lifts a burden from us. Maybe you have experienced the freedom of forgiving someone, even someone who didn't deserve it. Many times forgiveness is not deserved, but it can be given anyway. (Richard Rohr's ideas in What the Mystics Know have challenged me.)
Sometimes we are angry, not at a person, but at a situation or a circumstance--a slow driver, a car repair, bad weather, a missed opportunity.
Many have noted that life is not fair.
But have you ever forgiven life for not being fair?
Instead of holding onto bad feelings about whatever it is, you can just forgive everything and everyone. No longer holding reality accountable for being against us can give lots of freedom.
It might even contribute to happiness.