It's like discovering you missed the turn when your mind comes out of the chain piecing "haze" to realize you should have "turned right" back at that gas station 8 miles back! I do it all too often. I'm a big block piecer and longarmers everywhere are my best friends! Let's don't think about how this must feel to my wonderful longarmers. I am into "production" for my charity quilts so not getting the seam together at the first shot can really interfere. I have looked up (awakened!) to discover a couple of dozen big blocks not joined or more.
Still I smile, drop back and punt (as my football player husband called it), replace the bobbin, and reestablish my process. BECAUSE it beats the heck out of ripping out even one seam! I hugely dislike unsewing.