Well...there is a Ben Franklin type Poor Richard's Almanack view implicit in this question, based on a universal-utilitarian, time-value-of-money morality.

So my answer is bracketed within a BIG (HUGE, MONUMENTAL...) "If": A use of time is foolish if and only if it is foolish with respect to YOUR ongoing life story.

This is a much looser view of rationality than behavioral economics/"predictably irrational" etc. You can be acting in completely insanely dumb ways from somebody else's perspective (especially those darn "paternalistic libertarians" who want to impose their view of rationality on the rest of us artistically insane people), but as far as I am concerned, it's only foolish if you decide it is foolish.

And yes, you are allowed to go meta and be foolish anyway, just for the hell of it, because it makes your life more interesting.

If folding laundry is your calming-down ritual, then by all means weight it and value it appropriately. If you get a kick out of parallel parking and the game of finding that one great spot, go right ahead and hunt. But if not, yeah, might help to get a better handle on your sense of time and value (in the sense of subjective utility, not money).

With that long "If" out of the way, some tips to remain cognizant of the value of YOUR personal, subjective, narrative sense of time.

1. Understand your "time personality" ... read the Zimbardo/Boyd "Paradox of time" book to understand how we subjectively perceive time. In particular, get a sense of how your perception of time changes with your emotional state and business level. Take the Zimbardo Time Perspective Inventory (ZTPI): http://www.thetimeparadox.com/su... (note, I have serious metaphysical issues with the test, but it's a good starting point for introspection)
2. Understand the idea of "Time Cultures" by reading Robert Levine's brilliant "A Geography of Time" (http://www.amazon.com/Geography-... ) and understand why what might seem like "time wasting" in North America might be viewed as an excellent use of time in Mexico or Japan.
3. Get attuned to your bodily rhythms. Read any good book on chronobiology. I recommend Russell Foster's "Rhythms of Life" (somewhat technical, http://www.amazon.com/Rhythms-Li...) and/or Jennifer Ackermann's "Sex, Sleep, Eat, Drink, Dream" (less demanding, http://www.amazon.com/Sex-Sleep-...)
4. Read Keith Johnstone's "Impro" (http://www.amazon.com/Impro-Impr... ) to get a broader, artistic understanding of time, within the context of play and narrative. This will serve as insurance against you taking a literalist "time is money" view. You cannot, and should not, view a weekend curled up with a mystery novel as "so many billable hours lost."
5. This one was HUGE for me: buy a non-traditional clock. I have a 1-hour hourglass on my desk. You can get sundials, waterclocks, timed candles that burn down at a particular rate, even garden plans that help you grow flowers that bloom in different seasonal ways, providing unusual markers for your sense of time.
6. Stop wearing a watch. When you need to be on time in the clock-time sense, look at your cellphone or something.
7. And finally, if you need help putting all these ideas together, let me modestly recommend my own book, Tempo, http://tempobook.com ... to be released March 2011.