The Live Like You Were Dying singer wed hitmaker Hill in 1996 and the couple has three daughters together.
But McGraw confesses he would be an alcoholic mess, if not already dead, if he hadn't settled down when he did because his rock n' roll lifestyle was spiralling out of control.
He tells People magazine, "Right before I got married, I was a full-fledged rock star... (If I hadn't met Hill), I'd be dead...
"I would have partied too hard. I might have caught myself somewhere along the way and put the brakes on. I don't know if I would have gone (to rehab); I don't think I could have been talked into that during those times.
"Faith saved my life in a lot of ways -- from myself more than anything. I can go down a dark road sometimes, when you're not feeling good about yourself, and she pulls me out. My wife makes me a better man."
McGraw will celebrate two years of sobriety early next year (10) after kicking the bottle and his occasional penchant for cigarettes for good for the sake of his family.
He says, "I was never a smoker. When I drank, I smoked a little bit. I don't smoke at all now and haven't since I quit drinking.
I'm not a moderate kind of guy. My last drink was probably a year and nine months ago. I didn't do a 12-step program (rehab); I just stopped... It was the right thing to do."
Photos: Tim McGraw through the years