Why I shouldn't seam when slightly distracted

I'm through with both the front pieces and the back of my Cache Coeur. The next step is to Kitchener stitch the shoulder seams, which I did during Monk this evening. I got done with the one seam, held it up... it was a lovely seam, except that I had sewn the left front piece to the right side (and by "right side", I don't mean "correct side").

D'oh!

At this point, I had a good laugh and smacked myself. My theory on knitting projects is that any easy project will have at least one thing go wrong to make up for the lack of difficulty. Knitting karma, if you will.

So, the seam has been ripped out, and I'll have another go at it tomorrow (because right now, it's bedtime).