@GusC hit it on the mark, and I also wanna add that growing up also means facing your obstacles head on and at your own pace.
Let's be honest, adulthood is hard, and it can be harder when you have to deal with a lot on your plate. That can be family, mental health, finances, children, social expectations. Sometimes, you go into it not really prepared, no one bothered to prepare you, and yet you're expected to "adult"
But...from what I've seen and experienced...no one's ready to "adult" but you become "grown" when you accept that. Being an adult comes with accountability, responsibilities, and other things we have to handle. And those things can be made harder based on who we are and what we experience. But..when we accept that and face it head on, it slowly makes it that much easier, and overtime, you get your flow.
It's a process that can't be rushed. Luckily for us, we're adults longer than we are children, so we've got a good while to get comfy.
I'm a young adult, so I haven't experienced most of what's to come my way. But I think I'm grown in the sense that I'm ready to accept that things will come my way, both good and bad. Probably won't be ready for it when it comes, but I'll get there.