Albert Einstein's definition of insanity was, "doing the same thing over and over and expecting different results."
That's also the literal meaning of Sandler Rule #9, "every unsuccessful prospecting call earns compound interest."
In sales, we take for granted that we will fail more often than we succeed. So on the surface David Sandler's rule about unsuccessful prospecting should give us hope that the more times we fail the closer we get to a sale.
As Sandler-trained salespeople will tell you, hope is a terrible thing.