Group Therapy: What Little Thing Have You Done That Made You Think, “Wow, I’m So Not Smart”?

Have you ever done something SO stupid you thought, "Wow, Ia m SO not smart?"  We've all been there.  Reddit.com asked their users this question and this is what some of them had to say:

1. "Someone told me their birthday was on Friday the 13th this year.  I started looking through an online calendar to see if I'd ever have a Friday the 13th birthday.  After looking ahead 50 years, I realized my birthday is on the 18th... so no."
2. "I wanted to test the voicemail on my new cell phone, so I called it from my house phone.  Then I answered my cell phone and said, 'Hello?'"
3. "I ordered a big meal for my family at the Burger King drive-thru, paid, then drove off without the food.  And I didn't realize it until I got home and everyone asked me, 'Where's the food?'"
4. "When I was in high school, my friend was driving cross country, and I asked if he was driving all the way up to Canada to get across the Mississippi River.  He reminded me there's such a thing as a bridge."
5. "I once kept a dog turd as a pet for two months because I thought it was a cocoon."

So, The Rocker Morning Show wants to know... What little thing have you done that made you think, "Wow, I am not so smart"?