I just turned 19, and being honest, I didn't think much of it; but here are 5 reasons to not take turning 19 for granted.
You may legally be an adult, but you're still technically a teen.
Assuming you were considered an adult when you turn 18, you probably took full advantage of that title. Now that you've worn in the shoes of being an adult for a year, you want to stick your finger in the sugar bowl one last time. Nineteen is still technically a teen, so do what you most enjoyed doing in your younger teen years but with adult privileges and the excuse that: "I'm still a teen". Just be responsible while you make dumb decisions (might be counter-intuitive, but you'll thank me later).
You are at the top of the teenage food chain.
As cliché as it might sound, you can assert your dominance over younger teenagers cause you're older (which totally isn't a fallacy, *cough cough*). You can still relate to you're younger teenager friends, but you can still give them some banter by making sure everyone knows full well that you're the eldest.
p.s. Being the eldest also comes in handy in games that say eldest gets first play.
19 is a lot less suspicious than 18.
When you tell someone you're 19, it's easier to take your word that when you say 18. Although 18 and 21 grant access to new possibilities, they can also make people doubt you when you say that you're that age. When you say 19 though, it's more believable and not like you're trying to pull off an age that you're not in order to get access to things you shouldn't.
Less scary that turning 20.
In a way, it's nice that nothing really changes from 18 - you're still a teen, you're still a legal adult, and you don't have any extra expectations. When you turn 20 though, you're forced to start thinking about life now that you realize how old you are.
Another year, another birthday.
If somehow you can't resonate with any of the above reasons, just think - you're a year older, so you get another birthday. Since birthdays usually mean gifts and fun, you get to have another day dedicated to celebrating you being alive. Be thankful for how far you've come, what you have, and where you're headed.
Some ideas were stolen from: https://www.theodysseyonline.com/19-sick-age-19