Remember the old kung fu movies where a teacher would use the mistakes a student made to physically punish him? It was the harshness of the lessons that made them stick. Paying for a mistake so painfully engraves the lesson on your neurons—and sometimes on other parts of your anatomy.
Experience is a brutal teacher. But she's sometimes the best teacher; you certainly won't forget her lessons!
Your losses. Do you remember the deals you lost? Do you remember the deals you lost that you absolutely should have won? I remember all of them.
I remember one deal I lost: I had done the best discovery work of my life. I had built a solution together with the decision-maker. I had even gotten a verbal commitment—and a handshake. So, I was shocked and horrified to watch as a competitor swooped in behind me, made a promise to do something that the client and I had never even discussed and ran off with the business.
Now I never leave a sales opportunity without scheduling an appointment to resolve concerns. Had I done so then, I would have had a chance to respond to my competitor's offer. (Happily, I took back the account six months later.)
Your mistakes. How about your mistakes? We've all made them. On one call, I brought an inexperienced person from my team to a sales presentation. As soon as I was done outlining one of our procedures, she opened her mouth to describe a different procedure and confused our dream client. Once it was out, I couldn't put the genie back in the bottle.