Historically sitting on cash is a terrible decision a majority of the time, it's not even close. Without knowing you, your chance of correctly timing the peak and the bottom of the market is simply abysmal. The market may crash tomorrow, but it probably won't.

Let's say by incredible luck you manage to time both of these events perfectly, then what? There will be other crashes in the future, that's a certainty. And you won't be able to time all of them.