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Advice on strategy for when to sell
It's impossibly difficult to time the market. Generally speaking, you should buy low and sell high. Picking 25% as an arbitrary ceiling on your gains seems incorrect to me because sometimes you'll want to hold a stock for longer or sell it sooner, and those decisions should be based on your research (or if you need the money), not an arbitrary number. To answer your questions: If the reasons you still bought a stock in the first place are still valid, then you should hold and/or buy more. If something has changed and you can't find a reason to buy more, then consider selling. Keep in mind you'll pay capital gains taxes on anything you sell that is not in a tax-deferred (e.g. retirement) account. No, it does not make sense to do a wash sale where you sell and buy the same stock. Capital gains taxes are one reason. I'm not sure why you would ever want to do this -- what reasons were you considering? You can always sell just some of the shares. See above (and link) regarding wash sales. Buying more of a stock you already own is called "dollar cost averaging". It's an effective method when the reasons are right. DCA minimizes variance due to buying or selling a large amount of shares at an arbitrary single-day price and instead spreads the cost or sale basis out over time. All that said, there's nothing wrong with locking in a gain by selling all or some shares of a winner. Buy low, sell high!