When Justin Moore takes the stage, opening for Brad Paisley on the dynamic H2O tour, he looks as comfortable as a cricket in a cornfield on a hot August night. He rolls through his hits with the greatest of ease -- 'Smalltown USA,' 'Backwoods,' 'I Could Kick Your Ass' -- with energy to burn. But when he begins the poignant song 'Grandpa,' which he co-wrote with Jeremy Stover and Jamie Paulin, his demeanor reflects the raw, personal emotions one associates with the loss of a beloved member of the family.

During the song, Justin takes a moment to point to the heavens, signifying that his beloved grandpa, the late Tom Moore -- whom he affectionately called PawPaw -- must be up there watching.

When his grandfather lost his battle with cancer in late Nov., '09, Justin's world got a little smaller.

"I unfortunately lost my grandpa back in [November] after having the best year in my career," Justin tells The Boot. "It was kind of unexpected. It was my dad's dad. He actually retired out of the Navy. He unexpectedly died about three months after getting cancer. It beat me up pretty bad. One of the coolest moments of my career was getting to play that song at the Grand Ole Opry with him sitting back stage watching me, not knowing what was going to happen in the next few months. That's something I'll never forget."

So, how special was his grandfather?

"Not to be cliché, but he was my hero," Justin says with a sigh. "We all have a handful of folks that we can't imagine our lives without, and he's one of those to me. He taught me how to hunt and fish. He taught me everything. I'm real close to all my family -- especially him and my parents. The only way to look at it to get you through is that he's better off than we are, in my opinion."

Singing 'Grandpa' helps Justin resolve some painful memories. "I had a show the night he actually passed away, and they told me he'd be fine until I got back. We pulled into the gig on the bus, and I got a call that he had passed away. We went in and played the show that night because that's probably what he would have wanted me to do. You think that song would get easier and easier to sing, but it seems like it's getting harder and harder, especially with having a daughter now, seeing my dad around her and really understanding even more about how much grandparents mean to you."

Justin plays tonight, May 28, in Kansas City, Mo., and will be at the Atwood Music Festival in Monticello, Miss., on Saturday, May 29.

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Justin Moore on AOL Music