I was trimming a draft horse's foot in Spokane and realized my rasp angle was off by about 15 degrees

Spokane is a good example because fresh eyes see things we miss. That kid hearing the rasp sound off proves sometimes our muscle memory gets lazy. I had a farrier tell me once after 20 years his own son pointed out a grip change, and it fixed his wrist pain for good. Getting defensive over a basic observation means you stop learning, even from a kid.