Seriously, unless you are an indexer and let the other players do the rebalancing between winning and losing stocks for you, if you own individual stocks, you have to know if a stock prospect has changed, and it's time to move on. Or many times, if a stock becomes overvalued and the crowd clamors to buy, buy, buy at any price, it's also a good time to "let them have it".
Many years ago, I read a memoir by John Neff, a successful MF manager at Vanguard who ran Windsor fund. Neff's style was value investing, meaning he would not chase growth stocks.
Neff said he could not and did not expect to buy exactly at the bottom, nor to sell at the top. About selling, he said he always "sold too soon". He said there was nothing wrong with leaving something for the next guy.
I looked on the Web, and found out that this philosophy predates John Neff.
“I will tell you my secret if you wish. It is this: I never buy at the bottom and I always sell too soon.” – Baron Rothschild
Neff retired in 1995, and died in 2019. I bought his book, which was published soon after his retirement. Just looked around the house, and have not located it.