I only fix it if it bugs me. Some mistakes like chopped off points don't bother me. But is a piece is totally turned, I can't stand it. One time I didn't see a mistake till after it was totally finished and completed. Rather than disassemble or leave it. I made another component of the block, fused it over the mistake and requilted it. It was a hanger so it doesn't show at all and my mind is at rest.