What have you done that makes you cringe? Please, no failed marriages,
drug or alcohol problems, bad personal relationships, financial
disasters, poor employment choice, etc. There are millions of those.
Just something that was stupid but harmless. In other words,
lighthearted, nobody got hurt, but incredibly dumb.
  Here's my own example. When I was a 27 year old unmarried chemist
with a fine job, a fellow chemist and I decided that laundry
detergents were vastly  overpriced, which was true. All we had to do
was make the same stuff in our basements. The concepts of marketing,
advertising, distribution, FDA approval and a host of other
constraints never crossed our innocent minds. We purchased bottles,
fragrance, and detergent chemicals. If we sold 1000 bottles door to
door, we might have had a profit of $50 each. The reality that our
sales would be zero finally sunk in. I had a lot of bottles for years.
What's your story?
monroe22

Howdy, Monroe!

I have done lots of really dumb things, but this one stands out.

In August 1969, shortly after I graduated from college, I had a brief
and disastrous venture into the world of mead-brewing. I had always
been interested in mead, a honey-based fermented beverage that is
frequently mentioned in Norse and Celtic literature. I came across a
recipe for brewing mead, and I spent a long, tedious day whipping up a
big ol' batch. I bottled it in brown screw-top bottles and
hand-labeled the bottles in beautiful calligraphic script. I gave my
mead as a gift to several special friends.

One of my friends was a Celtic Literature professor at the University
of Tulsa. I visited his office and proudly presented him with two
bottles of my homemade mead. He was delighted, and he thanked me
profusely.

I kept about a dozen bottles for myself, in a kitchen cabinet. 

About a week later as I was lying in bed, I was shocked to wakefulness
by the noise of what sounded like gunfire. Loud banging noises were
coming from the kitchen. I rushed in and found that every one of my
bottles of mead had exploded, and the interior of my kitchen cabinet
was coated with honey-yeast goo.

The recipe that I used had failed to mention that as the mead aged, it
would produce expansive gases which would require the use of corks
secured with wire, NOT tightly capped bottles. Uh-oh.

I telephoned my professor friend to warn him.

He knew.

My mead giftie had exploded on his desk, and a stack of ungraded
summer-school term papers had been turned into sticky mush by the
explosion.

Sometimes when I'm feeling all bursty-proud of my superior intellect,
I remind myself of this incident. It's always useful to have a good
"stoopid story" with which to bludgeon one's ego. Fortunately for me,
my ego will never need to go unbludgeoned as long as I can recall the
episode of the mead bombs.

Best regards,
Pink

Pink: Another winner...your story is marvelous. Everyone has overdosed
on stupid pills one time or another.
monroe22

The dumbest thing that I have ever done is to congratulate the
Questioner and the Answerer on this occasion.

I don't know what came over me.

Maybe it was something I ate that didn't suit me.

The Dumbest Dummy ... EVER!

I have selective amnesia about several of the dumbest things I have
done (all personal interaction; the other dumb things don't come near
being "dumbest"), but every now and then one of them comes to mind  -
blush, whistle ...!
Questions like this reinforce the amnesia  - but probably only till I
click on "post comment".  :-)

This story made me think of this question:

From gold to silver, just like splat
http://www.mercurynews.com/mld/mercurynews/sports/13899796.htm

When I was like 8 I mixed a whole buncha stuff in a gatorade bottle
and left it on a shelf. I came home from school one day and like 10
seconds after I got in it exploded and this nasty rotten grey stuff
splattered everywhere. It turns out I put in large amounts of yeast
and sugar. It must have been pretty powerful to break through the
thick plastic of a gatorade bottle.

Wow, yes ... It's only just occurred to me ...

When I was a kid (maybe 7 or 8) I used to enjoy visiting an uncle who
had a farm and I particularly liked playing in his loft that was
packed with interesting stuff that kid's like, including a blow lamp
and a can of petrol.

Well, I started playing around (as you do) and before long I had the
entire loft ablaze.

I dashed down the ladders into the house and yelled 'Fire! Fire!' but
all that the older folk did was laugh. They thought it a great joke.

Then Uncle took a look ...

For some reason I was never allowed in the loft again.

Oooh, that shocked me out of my amnesia (hi Dr. H. Pope, another question).
The last time I was in a loft, 40+ years ago, drunker than I thought,
and not alone, I forgot I was in the loft when I stepped through the
door that only had a ladder ...   Didn't break anything.

So, Myo ... You were 'not alone', eh?

Do tell ...

Did young folks in those days do what us young folks today do when we
take a young lady up to a loft?

Curious.

A gentleman shouldn't even ask, let alone answer; but not quite ...  ;-|

Today while I was making lemon pudding, I remembered another dumb
thing I once did. I had a set of metal canisters in which I stored
baking ingredients such as flour, cornstarch, salt, and sugar. Each
canister was a slightly different size, so I didn't bother to label
them, since I was familiar with the contents of each. But not familiar
enough, as I learned when I made a batch of lemon pudding using salt
instead of sugar. Ewww. It was like some sort of weird gelatinous
margarita, except that it didn't have any tequila in it, so I had to
face up to my idiocy while sober. ;-)

Oh no, Pink, not another illusion shattered!

You, a goddess and my ideal woman is human after all.

What next?