It's not 50/50 that you're right or wrong. The position in which I benefit on the stock market exists if the market goes back up after a crash. It has always done such, even after the great depression.
Presuming that past performance has a correlation greater than zero with future performance, the odds tell me that I win in an index fund over time, regardless of a crash. If the dollar ceases to exist, none of my bets matter whatsoever.
It has nothing, whatsoever, to do with fight or fight. If you invest emotionally and not mathematically, you do yourself no favors.