Ok..how about this one. Here you are, working in a retail diveshop. You just finish helping the last couple drop lots of money on 2 complete sets of dive equipment. And, they trust you...cause you are a professional and know what you're talking about. And they leave for that evening's boat dive very happy.
Now, remember, you work in a dive shop so therefore, you forget what its like to dive (off a boat at least...cause you are always working!) Well, believe it or not, a spot opens up at the last minute on this boat dive, so you close the store, close the register, and you stop at the house and get your gear to get to the boat before it leaves the dock.
You get there...breathe a sigh of relief..and get your gear set up. And you know what you are doing...cause you are a professional. Now...you look at your gear, and something just doesn't seem right. So you check your air...and you check your BC..and everything seems fine. Then you have your dive buddy check everything. You have air...inflater is hooked up...computer is working. Then the Captain looks at it and says "so, is this a new aerodynamic way to dive?"
Here, I..the dive professional..hooked up my gear backwards, with the tank facing away from the BC and the screw nob on the first stage aimed towards the back of my head! (Like I said, I didn't get out much, and I was "stressed")
The couple I just helped spend lots of money on gear just looked at me...and looked at their gear...and just, sort of smiled...and double checked everything!
That about says it all! (hangs her head in shame!)