If you’ve had a stock perform particularly well, you probably noticed that it accounts for a larger part of your overall portfolio than it did when you bought it. If it makes up an outsized portion of your portfolio, you might consider selling it back down to a lower weighting through portfolio rebalancing. This can help your portfolio maintain proper allocations and avoid having too much exposure to one stock.
But be careful not to rebalance too often, or you might find yourself repeatedly selling companies that are performing well and adding to ones that aren’t — a process some investors equate to cutting the flowers and watering the weeds.