A poor attempt to deal, Dr. Luskin said, “mirrors the fight-or-flight mechanism built in for how to cope with stress.”

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At the same time, he said, the converse is true: Full forgiveness can more or less reverse these negative repercussions of holding onto anger and grudges.

O.K., so getting over grudges is good. But how do we do it?

In broad strokes, full forgiveness has four actions, according to Dr. Luskin. But before that, we need to recognize three things: 1. Forgiveness is for you, not the offender. 2. It’s best to do it now. 3. It’s about freeing yourself — forgiving someone doesn’t mean you have to like what they did or become their friend.

From there, the first tactic is to calm yourself down in the moment. This can mean just taking a deep breath to collect yourself or going on a jog, but the idea is you want to slow down and collect yourself to create a little distance between what happened and how you’re going to react to it. “You have to counter-condition the stress response when it happens,” Dr. Luskin said.

Next, shift how you think and talk about the source of your grudge. “Change your story from that of a victim to a more heroic story,” Dr. Luskin said.

The final two pieces go hand-in-hand. Pay attention to the good things in your life “so you have an easy way to balance the harm,” Dr. Luskin said, then remind yourself of one simple truth: Life doesn’t always turn out the way we want it to. Combining those two ideas can “shift the ground, and it lowers very dramatically” your general level of stress. (For even more on learning to forgive, click here.)