Before we discuss the power of forgiveness, let's work on defining what forgiveness means.

If we rely on the definition as offered by psychologists, then it is…
a deliberate or conscious decision to let go of resentment toward someone, regardless of their deservedness.
The dictionary definition is a bit more simplistic. Merriam-Webster defines it as… letting go of the anger you feel toward someone.

Whichever definition you prefer, the point is that you let go of negative emotions and move on without holding a grudge.
 
Forgiveness is really about giving yourself peace of mind. It isn't about freeing others from their guilt or shame, it's about freeing yourself from anger.