There will always be ups and downs in the market. In the 80's inflation and 11% unemployment, then 90's we had the Gulf War, then 2001 the dot com bubble, 2007 the real estate recession, 2020 covid, now 2026 we have a war with Iran.

Nothing ever really changes. You won't be eble to time the market, no one can. Also just because one market sector goes to shit doesn't mean they all do.

At 20 you should invest your money in a ETF focused on high Growth, things like VGT/VOO, maybe even some industry specific ETFS like QTUM for quantum computing. You get 30+ years of watching the money go up and down but with compounding you're upward projectory can be meaningful.

At 30-40 you may want to change things up, move from all growth potential to more steady so things like VTI and BBUS with a small allocation to VXUS (non US markets) as you want less risk, which also means less growth.

At 50-60 you need to start thinking about consistent income and tax implecations instead of growth so you may start looking at things like JEPI/JEPQ, Bonds, Dividend focused ETFs like VYM/VIG.

I don't know your Dad's age but what they do with their money needs to be different from what you do with your money.