The Beaumont-bred crooner with the black cowboy hat didn't write the recent Top 10 country hit, whose opening line refers to St. Jude Children's Research Hospital in Memphis, Tenn., which treats children with cancer.
But the first time Walker heard the song and its Job-like quandaries, he said, "I got it immediately. There was no mistaking that the song would belong to my life."
No mistaking it because the 34-year-old Walker — who has sold 8 million albums, with 11 No. 1 singles, since his 1993 debut — was diagnosed in 1996 with multiple sclerosis.
No one would ever guess it, though, by looking at the strapping Texan, who takes a daily injection of Copaxone to keep his MS in check.
"When I was first diagnosed, it was the most broken that I've ever been. You know, I don't think faith is faith until you have to test it," said Walker, a Christian who will kick off a nationwide, 15-city "MS Road Tour" April 1 in Dallas.
"It was like, my faith lit on fire at that point," said the Houston resident, who is married with two daughters, ages 4 and 8. "I went home and I got on my knees and I prayed. I don't know how long I prayed and cried. I got my guitar and I played hymns I learned as a child."
The tour — an effort to call attention to the disease and raise money for research to find a cure — marks a remarkable transformation for a singer who first experienced facial spasms and numbness in his right leg and arm eight years ago.
For a long time, Walker preferred not to talk about the disease. He didn't try to hide it, he said. But he didn't bring it up either.
After meeting people with MS at many of his concerts, though, Walker's outlook changed.
They wanted to know about his experience so they could relate it to their own lives, he said. At the same time, he was surprised to learn that many people with MS don't treat the condition, either out of fear or ignorance.
"It's a serious disease and the worst thing you can do about it is nothing," said Walker, whose No. 1 hits include "If I Could Make a Living," "This Woman and This Man" and "Then What."
Last year, Walker decided to do something to help the cause.
He started the nonprofit Band Against MS Foundation to raise money for research. The foundation recently awarded its first grant, for $150,000, to the University of Texas at Houston.
The National Multiple Sclerosis Society recognized Walker in November with its "Ambassador of the Year" award — only the fourth time in the organization's 58-year history that it has bestowed that honor.
"There are many celebrities that will lend their names to organizations such as ours, and that's very important and very helpful," said Arney Rosenblat, the MS society's spokeswoman. "But sometimes they go beyond that point and they give of themselves as well. That is even more deeply appreciated."
About 400,000 Americans have MS, which starts with such symptoms as numbness, tingling and fatigue but progresses to difficulty walking and seeing and, in some cases, paralysis. It usually strikes people ages 20 to 40.
Some patients, including Walker, have "relapsing-remitting MS," periods of severe symptoms after which patients almost totally recover until the next attack. Other MS patients have the worse "secondary progressive" form, where the flares become more frequent, and they don't recover from the damage each one causes.
MS occurs when patients' immune systems go awry and attack the fatty layer of insulation, called myelin, that protects nerve fibers in the brain and spine, thus damaging or even destroying nerves.
In Walker's case, the disease brought him face to face with his own mortality.
"I think a lot of little things that bothered me before roll off of me like water off a duck's back," he said.
Now, he hopes he can provide "a small ray of hope" to people, like him, who suffer from MS.
"It's much more than an eye-opening experience," he said. "I just look out of a different window now. The window is much bigger now, and it's also raised up so I can smell the flowers."