I mean being in your 30s isn't all bad. I'm at a point in my life where I definitely enjoy my life so much more than I did as a teen or in my 20s. Mentally I'm more healthy than I ever was. I just really wish I had the physical body of early 20s me again. I got over colds so quickly, I bounced back from all nighters like it was nothing, good metabolism, felt fine after eating junk food.
It's kind of a twisted thing, I feel as a teenager I wasn't mentally in a state to enjoy life, and now that I'm ready to take on the world and live life to the fullest, I have this aging body. And i'm still pretty young, and my body isn't in that bad of shape, it just isn't the same.