the first decade of life is pretty much a write-off on account of extreme ignorance and ingratitude. i mean, come on! someone is meeting your every need, feeding you pre-cut veggie chunks and animal crackers, wiping your ass for chrissakes, and all you do is cry. next comes school - waah, waah, grade two homework sucks. yeah kid, try the real world, where you're expected to actually pay for those dinosaur shaped chicken nuggets.
the second decade is wasted on worrying about the size of your breasts/kneecaps/balls/zits/video game scores and/or the presence or absence of secondary sexual characteristics/parties interested in exploring the wonderful world of "i'll show you mine if you show me yours"/parties interested in dating/kissing/fondling. you are never at ease but are busily hating your parents/life/teachers/skin. all very painful and deep. yawn.
the third decade rocks. a little less stress, a little more self respect and self awareness. granted, you look back on the second decade and miss the lithe physique you spent so much time hating, the metabolism-in-overdrive, and the parties characterized by wild abandon and genital herpes (just kidding), but overall life is good. except on the horizon looms the realisation that you are about to enter middle age, or the fourth decade.
the fourth decade (and this is all hearsay from here on in) is like the third but with more wrinkles, slower metabolism, divergent sexual needs along gender lines, and the subsequent emergence of the cougar phenomenon. more stuff has been acquired, younger spouses have been interviewed and purchased: you still have your vigour, which, coupled with a stable income, really brings the trixies running.
the fifth decade is where it all begins to go wrong (according to today's boss - and, to be perfectly frank, my mom would back him up on some bits). the eyes, almost overnight, go. the knees begin cashing the cheques written by your youthful (read: stupid) exploits (see second decade). the male libido checks out of the hotel entirely and prostate problems move in. the breasts head south, the back aches can no longer be ignored, and the downward slide begins.
the sixth decade is more of the same, only worse. granted, my father just ran his 40th marathon in his 61st year, but i think we can all agree that this is hardly what you can hope for, especially given some people's predilection for yummy things in large quantities washed down with vats of liquor. mental faculties begin to flail and fail and you begin to drive like a frightened old person. the face seems to have become covered in slowly melting dough so it's a good thing the eye sight keeps getting worse.
you don't want me to go to the seventh and eighth decades because it's just too depressing, although there is the bonus of no longer giving a shit if you fart in public or if your pants are pulled up to your armpits.
then you die.
so basically out of all this time allotted to us, we get to enjoy and appreciate roughly 20 years. 20 years out of 80. harrumph.
not what i signed up for, let me tell you, not it at all.