The advice that I follow is to take a statistical approach: Invest in everything. Let the losers wink out on their own while receiving the benefits of the winners.

Short version: Invest in (1) Total U.S. stock market index, (2) Total world stock market index, excluding the U.S., (3) Total U.S. bond market index. The principles are (1) Asset allocation, (2) Diversification, (3) Rebalancing.

For a lot more info, see (1) "Bogleheads Investing Advice and Info" https://www.bogleheads.org/ and (2) "Bogleheads Wiki" https://www.bogleheads.org/wiki/Main_Page