Shuushin31 Mar 2004
I think it represents a good snapshot of a frame of mind in the moment just before one "grows up" (whatever that is) - this exact feeling.
You may be surprised, and perhaps relieved, to know that there is still a bit to go and you won't spend your entire life wishing for misspent youth.
As a slight aside, there is a recent study where folks aged 65 and older were asked what their favorite age was - 40-41 was the most cited result.