Hah! 18 is not old. 30 is not old. 40 is not old. "Old" is a state of mind, not how many times you've gone around Sol. I may be older than 95% of the members, but I am not old. Well-weathered maybe, but not old.
The good part is I am 40 with no wrinkles... being fat pays off in that way. I have all my hair and very, very little of it is gray... not enough you can see it without getting really close, but that's due to the Cherokee in my mom's side of the family. It is also the reason I cannot grow a beard worth spit.
Enjoy life, make something of it. You only come through here once, so there is no use in letting it go to waste.