18's a great age to be. Up until 21 getting a year older is actually something to look forward to. I realized on my 22nd birthday that it wasn't special; I was just older. And that's how my birthday since then has been.
18 is within the period where birthdays equal more priviledges.
I wanted to turn 16 so I could drive.
I wanted to turn 18 so I could vote and see R-rated movies unattended.
I wanted to turn 19 so I could legally drink.
I wanted to turn 21 so I could legally drink in the United States - ie: the "fully enjoy Las Vegas" age.
22 doesn't provide anything. You're just an adult. Still a young adult and likely still healthy and attractive and with many good years left. But you would rather be 21. At 22 you realize for the first time that it would be better to be younger than your current age than older and I found that hard to take.
Being 18 kicks ass so enjoy it. I don't really mind being 26 that much either but you're still at the age where you're looking forward instead of back and that's great.
And if fear of going to jail is a legitimate concern I would suggest that maybe you need to make some changes to your lifestyle.