Twenty years ago, Azim Khamisa's son was shot and killed while delivering a pizza. It was an act of senseless violence, the kind that keeps parents up at night.

Khamisa felt frozen by shock and grief for weeks. Then, a spiritual guide urged him to focus on forgiveness, encouraging compassion in the face of loss.

When Megan Feldman Bettencourt met Khamisa three years ago, she was amazed by his story. He had not only forgiven his son's shooter, but also worked with the man's grandfather to form an organization that offers nonviolence training in schools.

Khamisa inspired Bettencourt, a journalist who's covered grim topics like gun violence, genocide and war, to embark on a study of forgiveness, exploring how people have used it to find peace. The resulting book "Triumph of the Heart," which will be released Aug. 11, presents forgiveness as a skill that can be taught and highlights how people can use the practice to build a happier, healthier life.

"Far from being a single, earth-shattering accomplishment with an end-point, forgiveness is more like a regular habit or practice, like being optimistic or mindful or patient," writes Bettencourt.

With scientific research, reflections on her own experience and the stories of people who survived traumatic events, Bettencourt illustrates the transformative power of forgiveness. She concludes that letting go of old resentments is a path to better health and brighter days.

"Forgiveness, it turns out, is more about the future than the past," she writes.

Bettencourt spoke with us about her new book, highlighting the link between spirituality and forgiveness, and explaining why "I forgive you" are three of the most powerful words people say.

The interview has been edited for length and clarity.

Question: The subtitle of your book is "Forgiveness in an Unforgiving World." What did you mean by "unforgiving?"

Megan Feldman Bettencourt: The nature of the world we live in is that we get hurt. People die. Good people get terrible diseases. Innocent people get shot and killed every day. It's not a soft world.

Question: As a result of life's hardships, many people become cynical about forgiveness. Are they misunderstanding what it means to forgive?

MFB: There's a common misconception that forgiveness is weak. But now that I have really focused on getting better at forgiveness, trying to forgive myself and other people when we fall short, I know that forgiveness is absolutely not weak.

When I think about the people in the book, someone like the priest in Rwanda who was able to forgive the man who murdered his mother during the genocide, I know that their actions are anything but weak.

I also reflect on people who offer forgiveness to someone who is totally unrepentant. This is something that we think of as unexpected or even wrong. We think that someone should apologize. And if they don't apologize or show remorse, they don't deserve forgiveness, right?

It is absolutely easier, of course, to forgive someone who is remorseful. But what struck me as I reported this book were stories of people who offered someone forgiveness when that person was totally unapologetic. That's pretty incredible, and it's not the way we usually think of forgiveness.

Another big misconception is that if you forgive someone you have to reconcile, that those two things are synonymous. They're really not.

A lot of people are stuck with bitterness and resentment to the detriment of their health because they think that forgiving someone means inviting that person to Thanksgiving dinner. That's not true.

Question: Is offering forgiveness more about our emotional and physical well-being or about our relationship with someone else?

MFB: It certainly starts as an internal process in which we release resentment and bitterness. If we're talking about a large loss or offense, it involves grieving and letting yourself be angry when you're angry.

That's all very internal. But the way we feel internally, the way we think, manifests in our behavior.

This is why the seeking and granting of forgiveness is so key to any form of peacebuilding. If we forgive someone, we might not be friends, but we're not going to retaliate with vengeance or violence.

Question: Your book references many health benefits of practicing forgiveness. Which healthy side effect of forgiving surprised you most?

MFB: I think one of the strongest studies was one done by Robert Enright at the University of Wisconsin. He studied cardiac patients, and the group of patients whose treatment incorporated some kind of forgiveness therapy had better outcomes than the control group.

That's very interesting to me, because the mood research on how forgiveness lessens anxiety and depression isn't particularly surprising. But the impact on heart health is pretty impressive.

Question: What's the relationship between religion and forgiveness?

MFB: Most of us know that the world's major faiths, to one degree or another, address forgiveness. Studies have found that people who are religious tend to forgive more readily.

One reason for that is that it's taught. Another reason, and I think this is very interesting, is that forgiveness is spiritual.

For example, Buddhism, which does not involve belief in a particular deity, offers a set of practices to live by that includes mindfulness, or living in the present moment. It's hard to be ruminating about how someone hurt you or disappointed you 10 years ago, or five years ago or one year ago when you're being mindful.

The word "spirit," going back to the Latin root, means courage, vigor and breath. That means people who consider themselves spiritual (but not religious) can practice forgiveness. It means really anything that gives us breath, courage and vigor could be considered a spiritual practice.

Question: What are some practices like mindfulness that people might want to take on to increase their forgiving spirit?

MFB: One that I think is really simple and that I like is the practice of journaling and writing letters.

You might not ever show anyone (what you write), but if you're really irritated at someone or disappointed in yourself and feeling that horrible self-loathing that many of us feel on a regular basis, then you can write a letter to yourself or someone else saying exactly how you feel and why and what happened. You can declare that you forgive yourself or whoever it is that hurt you.

It's a really great practice, and it doesn't take much time. I try to do that fairly regularly if something comes up and I'm stuck on it.

One other thing I would suggest in terms of practicing forgiveness in everyday life is to focus on empathy.

It's really easy to get irritated with someone and forget that we often have no idea what people are dealing with. We live in a world now where you're seeing everyone's social media facade. It's easier to project a shiny, happy, "everything's perfect" picture.

But everyone is dealing with something. We have to remember that we never know what people are dealing with and why they're acting a certain way. For the most part, people are doing the best they can with what they have.

Question: Did your research and reporting on forgiveness affect your relationship with family members and friends?

MFB: I do think so. Hearing their stories about how they grapple with forgiveness was life-changing. I think there is really a power in sharing your story.

There's a special bond created when you're privileged to hear a story (about forgiving), and I felt it even with the people I spoke to who didn't begin as friends.

One of the things that I dealt with during my writing was confronting how I responded to feeling insecure when I was younger. I tried to put other people down to build myself up.

My oldest friend shared that I did that with her. I didn't remember acting that way. I felt so bad about that, because I wish that I could turn back the clock and change that about myself.

But I'm so glad, and so grateful, that through these conversations it was cleared up and I could apologize to her.

There are so many things we do that we forget about. It's so easy to go through life in a rush and overwhelmed. It's easy to write someone off and move on, to do something terrible and not address it.

The more we can reverse that (behavior), the better chance we have to make an impact.

Question: What do you want people to take away from reading your book?

MFB: No matter what happens, you don't have to be stuck with blame and bitterness toward anyone, including yourself. If the people profiled in my book can live without bitterness after what they've been through, then all of us can do that.

I hope that's an inspiring and enlivening takeaway for people.