When Tim McGraw gave up the firewater five years ago, it wasn't because somebody gave him an ultimatum . . . or because he hit rock bottom.  He just figured it was time.

He tells "People", quote, "I drank a lot from my point of view and I needed to stop.  I felt quitting was something I needed to do.  I didn't feel I had any moral high ground with my kids in the long run."

As we saw in those tractor tire workouts last summer, Tim replaced his alcohol high with grueling physical workouts.  He adds, quote, "Working out is a great way to go out on stage.  When I hit the stage, my adrenaline is going and I'm ready."