And then get a royal headache while trying to darn the mistake. If the actual word 'darn' - or something stronger - comes out of your mouth while doing so, don't fret. This is quite natural.
And enjoy your shawl!
I actually gifted this to my grandmother for Christmas. Gram's been doing plain feather and fan afghans for years and years*, and when I chose this pattern I did so for love of the way that it played with that old, old pattern. Gram loved it, and appreciated the work involved. In our family, knitting equals love.
*I don't really think Gram knits much else. We were delighted when we found a picture of Mom's first birthday and realized that Gram was working on a feather and fan afghan in the background!