To followup, I think the most useful advice was similar, but just to "suck it up".
I was a bit psyched by doing the next Break In B workout. Instead of the originally planned 2 days after the A, it turned into 3 days later (spent most of Saturday
sleeping because of rough week at work). But then I finally psyched myself up, went into the gym and said "screw it, I'm lifting this sh**." Tacked on slightly more weight, did it, and then moved on to the next exercises. Soreness was dramatically less.
So I think a huge part was just complete unfamiliarity with the exercise.
But now I need to re-readjust and go back to working on my form.
