We talk a lot about due diligence before buying—but how do you know when it’s time to sell?

We talk a lot about due diligence before buying—but how do you know when it’s time to sell? As a Beginner in Value investing and stocks in general, I find much of this subreddit is focused on the what stocks to buy, when to buy them, and why they are bound to grow. However a side of investing that not many discuss and is arguably as or more important that buying stock is knowing when its time to sell. I understand that writing a thesis and constantly updating it is a key aspect of assessing a company’s health. However, there is so much room for bias and nuance when talking about a company’s strengths and weaknesses that it doesn’t really give me much insight into when a stock should actually be sold-especially stocks that seem to be doing fine before they collapse. So, to the individuals who have been investing for much longer than I have, how do you go about selling stocks, and what systems do you have in place to determine when your thesis has genuinely broken, when the valuation no longer makes sense, or when it’s simply time to move on?