Board shears karma

I'm lucky enough to be just five miles away from the Minnesota Center for Book Arts and not one but two full-size board shears. Cutting book board (the preferred material for boxes and most book covers) is incredibly hard by hand and nearly impossible to cut straight. (Right, Sarah?)
My teachers would all totally and completely disagree, but I think that there is a karma involved in cutting book board "square." Sometimes I almost want to burn some incense before I start. It's pretty simple to cut a few covers for books at the shears, but more complicated to cut, for example, 20 of the same boxes at one time. You do the best you can, pack up the cut pieces and take them home to see if you did it all right. If not, the best thing to do is sweep them into the trash can and call for some more time on the shears. (It would be great to assemble the boxes in the studio, but studio rental is a little pricey.)
I was lucky during the lead-up to Craftstravaganza...virtually everything I cut was usable. But the week after I booked an hour on the shears and came home to discover that everything was off just enough that my boxes looked like the homes in Ron's neighborhood in Harry Potter.
Yesterday I went back to do the boxes again. I took big deep breaths, and tried to pay attention to what I was doing. Clearly, though, my karma was having a coffee break: I came home with 2 sets of "Side A" and no sets at all of "Side B."