One of these things is not the same...got to love a Sesame Street Song, right?  Not when it applies to your knitting though.
I had been finishing up my 
Cotton Reel Mittens which I realized why I don't knit mittens - they are like socks.  You have to make two of them.  I went into finishing frenzy - stupidly during a really exciting playoff game between the Broncos and the Ravens.
I bound off the thumb, wove in the ends and put on the mitten.  It looked great, right!?
So then I got out the first mitten and put it on and realized something was wrong - one of these things is not like the other...see?
Too many stitches on the left hand mitten...grrr.  It went into timeout overnight and the next morning I got to work.
Painful but necessary.  After carefully paying attention to picking up the right number of stitches, I finished the second mitten.  Two of these things are the SAME!
And I'm done with mittens for a while!