Deepak Chopra explains the healing power of forgiveness.
When you have a resentment, grievance , feeling of hostility towards someone or if you have any of the other toxic emotions like guilt, shame, depression or fear, these emotions release hormones such as adrenaline and cortisol. These hormones have effects on the cardiovascular and on the immune systems. You become immune compromised, even your platelets get jittery with the high levels of adrenaline and they start the clotting cascade leading to cardiovascular illnesses, heart attacks and stroke. On the other hand when you forgive and let go the burden of judgment, everything settles down and your body starts to return to homeostasis, which is self regulation and self healing.