No one, no matter what they say, has the ability to predict the future.
If you want to be smart about investing, you figure out your asset allocation and ride out any dips/crashes without trying to time the market. If you can't stand the idea of a short term (I consider anything under 5 years short term) crash/recovery cycle, then you should set your AA to be super conservative and lose out on growth in exchange for safety.
If you understand how the market actually works (short term volatility is not the same as risk/the losses aren't locked in unless you panic and sell at the bottom) then you'll be less likely to worry about market crashes or dips in general.
I'm in FIRE so a market downturn might conceivably be worse for me than someone still working and adding to their portfolio. But I'm not worried. I've already seen losses of over $50K in the last couple of years and fortunately become desensitized to losing large sums since I've also seen recovery. I know in any given year, I have a years worth of expenses for my emergency fund, an AA I can live with, and I'm not going to need 100% of my portfolio in any given year anyway... leave it alone and it will build back up eventually. Worse case scenario I get a part time job and leave the $ alone to recover for a year or two.