So I went to a hamburger place with some friends after a basketball game. After looking at the menu thoroughly, I made the most unhealthful decision possible and got a burger with word "X-treme" in it. It involved a lot of meat and toppings (and I did it one handed). But, the initial choice was not the one that was REALLY illogical. After I ordered this enormous slab of beef and vegetable garden in between two buns, I decided to get a root beer float. I guess the logic would be, "Well I got a friggin huge sandwich that will probably clog my arteries and stop my heart, so I might as well get something equally unhealthy and deliciously fattening to wash it down." This type of thinking makes no sense when we step back, but at the time it makes perfect sense.
It's like saying while I'm up on the edge of this precipice overlooking a lake, "I might as well jump...and jump without shoes." Or it's like saying, "Well I already chipped my tooth playing this game, so I might as well keep playing it, because that tooth's not coming back." Or, "I already have a stain on my shirt, so I might as well go mud wrestling."
(Remember what happened when Old Blue went mud wrestling?)
These actions seem plenty logical. But, strangely enough they are not. There really are a lot of great examples I could give, but I'd rather you give me a couple. Tell your best story in the comments.