As you know, the main risk when selling covered calls is that the underlying stock could fall in price. If you own a covered call position on a stock that plunges, the premium you received from selling the covered call will not offset much of your loss.
Fortunately, there is a strategy called a collar that can protect the value of underlying stock when you are selling covered calls. If, after selling a covered call, you believe that the underlying stock might tumble, and you want protection against a large loss, you can initiate a collar. Perhaps the stock has had a nice upward run, and using the collar strategy is one way to protect your gains. (Don’t forget that you can also sell the stock outright to lock in those gains.)