Noob here. I'm well aware of the simplest option purchases such as long calls and puts. However, as I look beyond that into strategies like Spreads, Butterflies, Condors,, etc, etc I see that it requires SELLING (shorting) puts and calls in combination with buying them. . (Straddles and Strangles seem to be the only other strategies that involve only buying/long put and call combos)

If I sign up with a ThinkorSwim account and eventually do some of these strategies which involve selling/shorting, what risks am I realistically facing regarding getting assigned the call/put if the other side chooses to exercise early?