Out of all of God's instructions, forgiving one's enemies and oppressors is arguably one of the most difficult things to do. Pastor Rick Warren of Saddleback Church knows it takes a lot of grace for people to let go of their angst, so he shared an inspiring story about forgiveness.

"In 1956, five American missionaries headed to the rainforest of the eastern Amazon in ​Ecuador on a second visit to the Huaorani tribe, which anthropologists said was the most vicious, violent society on the face of the earth. They had a culture of killing, and studies showed 60 percent of the tribe died by homicide," he shared on his website.

But after the missionaries got out of the plane, they were immediately speared to death by the tribe members. Two of these missionaries were Nate Saint and Jim Elliot.

A few years later, Jim's wife and daughter, Elisabeth and Valerie Elliot, and Nate's sister, Rachel Saint, surprised the world when they moved in to the Huaorani village to show love and forgiveness to those who killed Nate and Jim. Because of their compassion, Mincaye, the leader of the tribe, converted to Christianity.

After he did so, his men followed suit. "The kind of forgiveness that Elisabeth Elliot and Rachel Saint modeled doesn't make sense until you have been forgiven by God. Once you've experienced it, how do you forgive?" said Warren.

First, he said Christians must relinquish their right to get even. Then, they should respond to evil with good. People can do so by praying for God to bless their oppressors even if they've caused hurt. Warren knows doing these things will not be easy, so they should repeat these steps as long as necessary. Lastly, he said believers should rescue others with the Good News of God's forgiveness.

Warren also warned Christians that refusing to forgive can be detrimental to their health and spiritual wellbeing. "Resentment makes you miserable, and it keeps you stuck in the past. And when you're stuck in the past, you are controlled by the past," he explained. "Every time you resent something, it controls you."