What is ONE investment habit that is simple and effective that it surprises you more people don’t do it?

Hello world :)

What is ONE investment habit/strategy that is so ridiculously simple and effective that it surprises you more people don’t do it?

It could be anything - CDs, selling options, real estate related, etc. Nothing is off the table.

I am sitting on cash and plan on investing a good chunk of it in tech ETFs but curious about other investment strategies/habits.

Would love to hear from others!