Have You Never Been Mellow?

Why is it that the older one gets, the happier one is with doing nothing in particular in one's free time?

Is it the young who are restless, and have long lists of "to do's" which they need to achieve at the end of the day? Or are the old(er) just resigned to the fact that they can't do everything that they want to, and so should not fight the waves of life but to just go with the flow? Do we automatically become more mellow with age? And what exactly does "becoming more mellow" mean?

dictionary.com defines "mellow" as "having the gentleness, wisdom or tolerance often characteristic of maturity". That sounds right to me. Growing older makes one more tolerant of doing nothing, not rushing around in a harried fashion trying to achieve everything you have set out to do, crossing out achievements on your list. Is that due to wisdom, or resignation to one's fate, I guess the jury's still out on that. Or perhaps it's a wise person who is able to see what one can do and what one can't do in life and to resign oneself to the things that one can't do.

Just like the Serenity Prayer that goes:
"God grant me the serenity
To accept the things I cannot change;
Courage to change the things that I can;
And wisdom to know the difference."

And to that, I say "Amen".