Of course, most individual investors do just that: sell winners and hold on to losers until they reverse to break even.
One hundred years ago, the Stock Operator--Jesse Livermore--counseled against that. His advice was: "Buy what shows you a profit; sell what shows you a loss."
I'll grudgingly admit the Monte Hall problem is beyond my brain.
I do understand that one doesn't have to sell a stock to have a loss. If you buy a dog and he dies, don't you have a loss? Or do you have to put Fido's carcass on the market?
Wowser, I was looking into Stryker. 60 Times earnings! My somewhat similar Danaher Corp trades at 48 times. Nowadays one pays for a pedigreed investment.