I sold my Sun stock at the internet bubble top for $70 a share. A few months later it was $7. I think of that when I see PE ratios in the hundreds for Tesla, SpaceX and other AI stocks.
Good timing. But on the other hand if you had sold AAPL, MSFT, NVDA, ORCL, AVGO, ADI, KLAC, LRCX, etc at the Internet bubble top then you would have missed out on huge gains since then.
Scott McNealy had a few choice words in retrospect[1].
[1] https://news.ycombinator.com/item?id=40950311