The first thing that happens in a market crash is that nothing happens.
Your IRA does not lock. Nobody takes it. The custodian does not call. The account is exactly where it was on Friday, holding exactly the same number of shares it held on Friday.
What changed is the price tag. Which feels like the same thing and is not.
That distinction sounds like a platitude until you look at what it means mechanically. So let us look at the mechanics, the genuine risks, the real opportunities, and the specific situations where a crash actually does damage that does not heal.