"What's the last really stupid and careless "user error" YOU have made?"

On a very recent trip I tied a yellow ribbon on my suitcase handle as usual so that I coud recognize my bag quickly amidst all the others at the luggage pickup area of the airport. Since I have more than one suitcase, of different colors and styles, I tend to just look for a yellow ribbon on a handle. When I am tired from the flight and a long day I don't notice anything else, even the color of the suitcase I am grabbing.

Anyway, I grabbed a suitcase with a yellow ribboned handle and jumped in a taxi to the city. I booked into my hotel room and then went to unpack my suitcas. To my horrot, there was a lock on it that I didn't recognize. And a name tag of someone else, not me :-)

Getting out of that situation cost me to send this wrong suitcase to another city at my expense, and then go back to the airport to pck up my own - a very expensive little lack of awareness. Hopefully the cost suffered will mean that I am much more aware from now on in similar situations.