As Thomas Rhett sang in 2017, "Ain't it funny how life changes?" Since he released that song and the album of the same name, he and his wife Lauren have officially adopted their oldest daughter, Willa Gray, welcomed biological daughters Ada James and Lennon Love into their family, and are preparing for the arrival of their fourth child -- another girl -- in late 2021.

Looking back, the singer can't help but get a little nostalgic -- but also, be a lot grateful for what he's learned and how he's changed along the way. Rhett channels all of those emotions into his song "Growing Up," from 2020's Country Again, Side A.

Rhett co-wrote the song with Matt Dragstrem, Josh Miller and Josh Thompson while out on the road. Below, he shares the story behind "Growing Up," in his own words.

Man, you know, as many things I would love to tell my 19-year-old self, I probably wouldn't tell him, because then he wouldn't make the mistakes that he should have made to to come on the other side of those victorious.

But, that song, I'd had that title in my phone for a while, and I wrote that song with a few of my buddies out on the road. It's just like, every few years, there's, like, little dad-isms inside of me, where I wake up and I'm like, "Gosh, dude, you're getting old ... You are, like, wearing the front swaddle now with your kid on the beach -- you have officially moved into a different level of dad-ness."

That's kind of where the inspiration of that song came from, especially that first line. I'm still the kid I was, just a little less Jack in my cup. I noticed, every few years, there's certain things in my lifestyle that changes, and they just kind of remind me of like, man, you are just, every year, growing up and wising up and maturing a little bit. And I think a lot of my fan base has kind of been with me since I was, like, 19, and I think a lot of people relate to that song because we can all go back to our 19-year-old selves and remember how dumb we were, and all of a sudden, you're 25, married, with three kids, and you've got to grow up -- you're forced to.

I remember, even yesterday, I was driving in downtown Nashville, looking at these pedal taverns and these party buses with people just screaming, and I was like, "Man, if I was 19 years old, I'd probably be right there with them." And now I'm like, but I'm not -- I'm, you know, driving a minivan and taking my kids back home. [Laughs] And that's just kind of life these days.

[I notice] the juxtaposition of just kind of getting older and looking back at your life and going, never, in a million years, thought I would be where I am. But I'm so glad that I'm here.

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