This is your chance to share with the internet, all of your "lessons-learned-the-hard-way".
Here is my random assortment of things that just don't work for me:
Waxing. Technically speaking, this did work for me. I mean in the sense that the hair in question was indeed removed. However, it was not removed before I screamed in pain and nearly threw the waxing-girl across the room. My eyebrows are a bit scary, but I don't know how often I can make myself do that...
Yelling at my child that she should stop yelling so much. Ahem.
Thinking anything is safe in my mini-van parked directly in front of my home under a very bright street lamp. Anything... stolen items over the years include digital camera (Husband's fault!), purse, quarters in the center console, a NEW KIDS ON THE BLOCK tape, half drank can of Diet Pepsi, etc. In case I haven't mentioned it before -- Don't park in front of my house over night. JUST DON'T DO IT!
Magic Erasers. I know some people swear by these, but I don't like how they get all slimy and soapy right in your hand. Give me a washcloth and cleaner any day.
Going to the big box store without a well thought out shopping list. I still do this sometimes and unfortunately it never works out well. I always end up with entirely too many Little Debbies in my cart and not enough cans of green beans or diapers or toilet paper or... you get the idea.
Garage sales. I have never found that garage sales make as much money as the work they seem to be to put together. I'd usually rather just donate the items to the Salvation Army or Goodwill. And a charity gets some benefit as well.
So, what doesn't work for you? What have you learned thru hard life experience?