He's known for being surly when he has to be, but John Mellencamp can also be a pretty thoughtful and reflective guy -- as he is during a new profanity-laced interview that finds him laughing, "I'm the luckiest guy you will ever talk to."

Of course, that doesn't mean Mellencamp's started pulling punches on us. On the subject of the role vanity should play in a man's life, he scoffed in the pages of the March 2014 issue of Men's Journal, "I'm taking old age like a man. If I get a little belly on me...goddamn it, that's what happens when you get to be a certain age, that's the way a man's supposed to look. You're a certain f---ing age. Act it."

Mellencamp says he learned his lesson from witnessing Robert Plant's graceful entry into middle age. "I went to see him live a few years ago, and I didn't really know what to expect because of all his posing with his shirt unbuttoned during the Led Zeppelin days," he explained. "But today he just walks up, stands there, and sings his ass off. That's the way you're supposed to do it, man. Robert Plant taught me a f---ing s---pile."

Plant didn't teach Mellencamp the most valuable lesson of his life, though. That advice came from his grandfather, whom he described as "rough as a cob," and one day told him, "If you're going to hit a c---sucker, kill him." Chuckled Mellencamp, "The part he left out is that sometimes the c---sucker hits back. Hey, Grandpa! You forgot to tell me about this part. The world hits back."