Editor's note:The following column is excerpted from Shaka Senghor's new book, "Writing My Wrongs: Life, Death, and Redemption in an American Prison."

At age 19, Shaka Senghor was a drug dealer convicted of second-degree murder and sentenced to prison. But his story doesn’t end there. During a 19-year sentence, seven of which he spent in solitary confinement, Senghor turned his life around through literature, writing, and learning to take control of his thoughts and emotions. Today, he is a mentor to young men and women facing circumstances like his, a leading voice for prison reform, and a speaker at conferences like TED and Aspen Ideas.

In this story, taken from his book Senghor recalls how a letter from the family of his victim changed his life.

Earlier this year, I was rummaging through the footlocker where I store my journals, letters, and legal documents—the same locker that I carried from prison to prison for 19 years. I was looking for my parole papers when I came across a letter I had gotten from the godmother of my victim, nearly six years into my incarceration. It stopped me in my tracks.

The letter, dated July 31, 1997, arrived during a point in my incarceration when I was torn between old instincts and new possibilities. I wanted to change—but I didn’t want it enough. If you had asked the corrections officers around me that day if they held any hope for me, they would have at least hesitated. More likely, they would have laughed.

But not the woman whose family I had shattered by a bullet. She had hope. She believed that transformation could happen, even for me.

Dear James,

A few days ago, it was the 6th year anniversary of my son’s death. I call Chris my son (out of respect for the victim’s family and their privacy, I have changed his name) because he lived with me much of his life. I’m sure you remember him because you are the man who murdered him.

July 28, 1991 was a very difficult day for me and my family. I had spent 3 years being a caregiver for Chris’s mother, and she had just died of cancer in December. And then, six months later, I received the phone call that our son, Chris, was dead.

His brother was devastated. To this day, he says he didn’t only lose a brother — he lost his best friend.

Chris had a new baby son, only 10 months old. He also had two daughters. One is now in college, and although she is a very bright girl, she is having terrible bouts of depression because her dad is gone. The rest of our family tries to help her, but there is an emptiness in her life that no one else can fill.

What I want you to know, other than these painful things that you have brought upon my family, is that I love you, and I forgive you. How can I do less? Because God loves you, and I am a Christian, so I humbly follow his guidance. His word tells me (in the Bible) that He loves us all, no matter what we have done or how bad we think we are. And we are to love one another no matter the circumstances.

You may think your life is a mess, but you are special. And God is able to pick you up and help you to go on. He can clean up your messes, no matter what they are. God can be your best friend. Just approach him as a little child. Crawl up in his lap and let Him love you. He can fill that empty hole down deep inside.

Sincerely,

Nancy

The best I could do when I received this letter was take one small step. I wrote back.

When Nancy wrote again, we began a correspondence that continued for years.

Still, it would be half a decade before the change she hoped for would begin to manifest itself in my life.

We can never know the power that a word of kindness or an act of forgiveness will have on the person who needs it most.

And that’s the thing about hope. In the moment when you feel it, it can seem foolish or sentimental or disconnected from reality. But hope knows that people change on a timeline that we can’t predict. We can never know the power that a word of kindness or an act of forgiveness will have on the person who needs it most.

What I now know is that my life could have had many outcomes; that it didn’t need to happen the way it did. I was once an angry, lost teenager holding a community hostage to fear and greed.

Thousands of youth are making the same mistakes every day in cities all around our country. But we weren’t born that way. None of our children are born that way. And when they get that way, they aren’t lost for good.

That’s why I’m asking you to envision a world where men and women aren’t held hostage to their pasts, where misdeeds and mistakes don’t define you for the rest of your life.

In an era of record incarcerations and a culture of violence, we can learn to love those who no longer love themselves.

Together, we can begin to make things right.

Reprinted from "WRITING MY WRONGS: Life, Death, and Redemption in an American Prison" Copyright ©2013, 2016 by Drop a Gem Publishing, LLC. Published by Convergent Books, an imprint of Penguin Random House LLC.

Shaka Senghor is the author of "Writing My Wrongs: Life, Death, and Redemption in an American Prison." He is a mentor to young men and women, a leading voice for prison reform and a speaker at conferences like TED and Aspen Ideas. Follow him on Twitter at @ShakaSenghor.