Nothings reveals personal failures or bad investment of resources quite like a garage sale. A trip to the Goodwill is different--more anonymity, also the scant feeling of giving to the public good. As if the public is better off with the redistribution of my crap.
"Come see my failed fitness program! Come see what I haven't read, or couldn't fit on my body in my more optimistic days! Come see my half-hearted attempt at a hobby! Come see my fizzled-out work toward a collection! And get it at a low, low, humilitingly low price..."
The only reason I'm doing it is that the cash will be helpful, and my mind can rest a little easier with less clutter. That purging of junk is almost better than the cash. Almost.