What was a lesson you learned too late ?

Investors who are investing for 20+ years, what was a lesson that you learned too late? Anyone else who is new to investing is welcome to contribute. I think for most people who started investing end of last year(2021), the biggest lesson might be :

DO NOT OVERPAY- a great business might not be a great investment at any price- {think about AMD, NVIDIA, Netflix, META, Adobe, and many other beaten down stocks}