"My biggest sales fail cost me a $400k deal and a commission check that would have made my entire year. To this day, whenever I think about this deal, I get a sinking feeling in my stomach. This happened just a few years ago, when I was working for a SaaS company that was trying to go from SMB (small and mid-sized businesses) to enterprise. They were willing to invest in order to do that. I had never sold to any Fortune 500 companies before, so I felt a bit like a fish out of water.