Marie Tillman speaks at Clinton School

Wednesday night, Marie Tillman, the widow of U.S. Army Ranger and N.F.L. star Pat Tillman, spoke at the Clinton School of Public Service.

Pat Tillman died in 2004 when he was killed by friendly fire in Afghanistan.

In her new book, The Letter: My Journey Through Love, Loss and Life, Marie Tillman talks about the "just in case" letter her husband, Pat, wrote her before going into combat, only to be opened if he did not return.

"It was something that he wrote his first deployment to Iraq. And then, he returned home safely and left it there and said this is in case I don't come back the next time. It's one of those things that you never talk about. So, it was sort of this amazing gift that he had left behind, but at the same time, something I wish I never had to open," says Marie Tillman.

Eight years after friendly fire killed Pat in Afghanistan, Tillman travels the country, sharing his legacy through the Pat Tillman Foundation, funding scholarships for military members and their spouses.

"I hope that somebody that's going through something difficult would be able to connect with my experience in some way and see that, you know, things will get better," says Marie Tillman.

For Tillman, things are getting better. She recently remarried, had a son, and moved to Chicago.

"One thing I definitely have learned, you can't always predict what will happen in life, but you can decide how you're going to take all those things and what you're going to do with them," says Tillman.

Tillman put his football career on hold to serve in the military following the September 11 attacks. Initially, the military said he died in enemy fire, then it came out he was killed in friendly fire.

Marie chooses to focus on her foundation and the good it's doing. So far, the Pat Tillman Foundation has invested more than $3.2 million in financial support in 230 scholars.