In “We Don’t Sell Saddles Here” Stewart Butterfield elaborates on the importance of looking hard at your results and finding the things that do not work. Stewart’s message reminds me of this magnificent scene in Whiplash with Terence Fletcher (played by J. K. Simmons), a cut-throat instructor in a music conservatory who will stop at nothing to realize a student’s potential. Justifying his, very mildly said, harsh way of teaching Terence explains to his student: