Assuming the markets keep working like they have for 100+ years (this is a key assumption):
It's damn difficult to call tops and bottoms. Unless you have some proven and demonstrated way to do that, you are better off to just stay in the market. The drops are scary but historically the market comes back. And you might not, if you don't get back in at the right time.
I've been an active trader for almost 25 years. I ran a very successful commodity fund in 2000-2001, trading $10M of client money, returning 35-40% to our clients after all fees. And in spite of that experience, I can't call the market for beans. Instead I build models that call the buy/sell signals for me, and I mindlessly do what it tells me to do. That works very well, FOR ME. If you have a model like that, and if you have PROVEN that it works, then follow it. If you DON'T have a model like that, then you DON'T have any proof of your ability to beat the market. Which means you almost certainly can't. Don't try. Sit tight, buy the dip if you have spare $$.
Now if you DON'T think the markets will continue to work like they have for a century, you might make a different decision. Japan's market topped out in 1990. It lost 75% in the next 15 years (that would put a dent in your lifestyle!), and 30+ years later it's still 25% below the 1990 high. If you think our markets are going to do that, then yeah, "sit tight" might not be the best advice.
I expected a Japan-style crunch in the 80's. The Dow had gone sideways for over 25 years at that point, and everybody expected it to stay in that channel. That's what I thought too, and when it broke out in the 80's I rode it up a bit, then got totally out to wait for it to return to the channel. Which of course it never did. In the next 15 years I missed ***800%*** growth in the Dow, 13% a year, waiting for that pullback. Finally I said "This is insane, I'm missing so much growth!" so I jumped back in. In late 1999. Guess how that worked.
Unless you have PROVEN your ability to call the market highs and lows, don't try. There's a very high chance that the market will continue its incredible performance. 90% of professional money managers can't match the S&P500, and you probably can't either. There will be dips, there will be long sideways periods, but chances are you'll lose more by trying to beat it.