Interesting comments at Lifehacker's post on what's easier when you're younger.
Mornings after the night before.
Getting arrested. If you're not dealt with as a juvenile, people will call it a youthful indiscretion.
Quitting your job and driving around the country with your friends.
Falling back on a safety net.
Crying your way out of problems.
Still experiencing the feeling of invulnerability.
I would add:
eating anything you want and not gaining weight.
believing that life is fair
believing that you're entitled.
biking 50 miles one day and 50 miles the next and not needing Advil.
thinking that you're always going to love your tatoos.
having summers off to do whatever you want.
believing you won't survive a break-up.