I cannot stress this enough buddy....it...is...just...a...number. You always have been, and always will be, as old as you feel and as old as you "think".
I, myself, have had a few ups and downs and even at 17 and a few times in my 20's, I felt like I was 100. I let friends of mine, who happen to be gay guys, scare me about turning 30 when I was 17 years old. They basically stated that they knew they'd commit suicide before they turned 30. "Why?", I asked. Their answer was that in "gay years" that age was the beginning of "old" and no longer young, beautiful and attractive to the guys they were attracted to. So, basically a bunch of bullshit that fooled me for a year or two and I fretted about it, convinced that I had 13 years of living THE LIFE left.
To this day, I have more days that the 17yo in me is there and feeling like he can do anything and looking as good as he ever has, than I do feeling old. Granted, even when you take the best care of yourself, things age, but I treat it sort of as a reminder to slow down "just a tiny bit" and smell the roses...take time to enjoy what you've done, where you've been and where you're going and what you're going to do. Sort of like a scar from a childhood injury...sometimes its good to stop and look at it and remember ALL the shit you've done and been through and realize you are still here and going strong. It's pretty empowering buddy.
By the way, I'm 51, soon to be 52 in a few months and the 17yo in me is still here going strong. Live life and fuck the numbers. And as a side note, those that want you or don't want you, based on your age and not on the simple fact that they are attracted to you, really are not worth having in your life anyway.
OH! and....DRINK LOTS OF WATER...IT IS the REAL Fountain of Youth you've heard rumors about.
enjoy it!! 
