What is the definition of insanity?

One could say that the definition of a insanity is doing the exact same thing over and over again, and expecting different results. However, if that’s true, then aren’t we all crazy then?
After all, there’s no secret that our stock markets have crashed various times throughout our history. Sure, you can argue that we’ve always managed to pull out of it before, but the results are hardly different, as the cycle continuously repeats itself. Where the most ruthless and cut throat businessman can make it ahead in Wall Street, while the honest man gets left in the dust.

Lines from Wall Street.