How come my brain gets a vacation if I don't?

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People have their blood drawn from time to time.  And when they do, if they are an adult they are usually familiar with which arm is better for an easy stick and good blood flow.  Er .. at least they know which one usually works the best.  As do I.  So when I had to have blood drawn the other day I sat down in the chair and offered up my left arm.  "The vein is sideways but it's the one everyone uses so this is the side."  


The gal did the stick and filled one tube but on the 2nd tube she wasn't having any luck.  "Wow, this has slowed wa-a-a-y-y down, not getting much now."  She kind of moved the needle a bit inside the vein which triggered my internal squeamish switch and I had to talk myself out of getting light headed and freaking out.  Finally she decided to try the other arm.  On went the band-aid and in when the needle in my right arm.  "Oh that's better."  She said, "It's filling right up." 

A minute later I was done and walking out with a band-aid covering a lump of gauze on each arm which caused a little girl to gape in horror as she waited her turn.  Sheesh!  And as I reflected on it later I realized - I had given her the wrong arm.  


Which begs the question, where does my brain go, sometimes?  Does it just check out and some other thinking (or non-thinking) device takes it's place?  I mean - it was instinctual - here - this is the arm, use this one.  


Sometimes I just have to ask WTF??

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