I had a hard time to convince my friends and co-workers in 2000. How can you tell the lottery winners not to buy lottery tickets? We do have many rocket stocks today. From my books, I recommend to use trailing stops.
From an article about the entire internet company can fit into
the conference room of a Fortune 500 company with EQUAL market cap, I
switched most of my sector tech funds (100% from my annuity) to
traditional sectors (better to cash or even better to contra ETFs not available at the time) on April 5, 2000.
Luck or skill - you decide.