This Aging Thing Won't Stop Happening!

I'm 33. Almost 34. So far in life, I've achieved one major professional goal: never having to buy/wear a business suit. I kind of dress like a bum, which generally means not dressing my age. This is not to say I'm wearing daisy dukes or belly shirts (you're welcome), but I dress pretty casually and I'm pretty sure that's why people tend to guess I'm 23-26.
Despite the outward appearance, I frequently find myself thinking or saying something and then thinking/saying, "oh my god. I'm old. I just sounded like my mom (or dad)." At lunch today, I saw a kid, early 20s?, wearing a shirt that said, simply, "PARTY WITH SLUTS." I fought the urge to ask him how that shirt was working out for him. Then I thought, "Wait, what if that actually works with the girls these days?" I'm not saying that girls now are sluttier--most everyone I know has had their day--but maybe now they advertise it? We were a little more discreet (one friend explained, "I'm not a slut, just slutty."). My next thought was, "your mother must be so proud."
So yeah, I'm old. I like the wisdom aspect. Otherwise, I'm kicking and screaming my way to higher digits.