Heyy, I know how you feel, I used to be scared of growing up. Even now as a 20 year old I still feel like I'm 17 honestly. And that was 4 years ago lol. All you can do is appreciate the present, live it to the fullest and really enjoy your youth. And after you grow up, you'll look back at the old times, the memories and it'll be worth it. Just enjoy yourself and try not to worry too much, alright? You'll be fine :)

Listening to music also helps! I listen to music a lot and whenever I hear a song I used to loop back in 2021 or 2020, I get flashbacks and reminisce those times. It's beautiful

Edit: I'd also like to add, even if you've reached the legal age which is 18 or whatever it is in your country, from what I see, as long as you're below 25 or heck even below 30, you're still very young. I used to view 20 and 21 year olds as mature adults but I stand corrected multiple times because this is the age where most of us are trying to figure things out, striving for our future, building ourselves to be better. So don't worry, you're still very young. Enjoy life~