What I might have done isn't what I would recommend to the general investor.
But this is what I have done during the dip, I moved some fixed income investments to equities, SPY specifically. I also took out a margin loan to put into SPY, I paid only interest for 3 months, and when it rebound, I sold and paid back the margin loan. I also rebalanced my portfolio.
The amount that I did was an amount I can afford to lose, which wasn't a lot.
I regret not able to do the same during the start of the pandemic. And I regret that I didn't have enough money during the great recession.
The key is, I'm young, and I got time, and with time, the S&P500 has been proven to be failsafe for 100 years.
But now, I don't think I will have enough time on my side to do things like that again.
EDIT: correction. S&P only has been around for 70 years.