It does seem time goes by faster. I'm 31 and it seems the last decade flew by. The last six years in particular once my older sis started having kids have zoomed past me.
I would hate to ask myself where I'd see myself in 10 years now. I'm sure I'd be off the mark.
I do have some stuff in common with my 21 year self like being a twin, Morrissey fandom, vegetarian, etc. but I'd never have thought I'd have parrots or work in a jail.
At 16 I never thought I'd make it to 30. Youth seems eternal in those days.
31 was old to me. Now 23 year olds are kids.
I read Moz saying living to 40 would show a lack of resolve once and he's well past 40.
It's good to eat our words sometimes.