No, look at the option chain, even if the stock blows past, say your 20 dollar written call, you can buy it back.
I understand it is complicated, I've tried to explain it on several occasions, I think there is also a thread somewhere here or on SI that I created.
So, last I looked, was hours ago, you could sell August 20 dollar calls for 1.60 and the stock was around 17.60
August 15 calls were going for about 2.80
See where this is going? You can cash in 1.60 now and if/when the stock gets above 20 you buy back the calls with a small premium leaving you with 1.20 profit, or 1.40 and you still have the stock.
If it never gets to 20, the calls die and you keep everything.
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