I can't think of anything specific. I just seem to intuitively have a nose for possible discomfort when I'm planning to do anything or when people are suggesting I do anything, and if it seems like it'll make me uncomfortable I either dismiss the idea or try to figure out some way of making it less horrible. So it's more discomfort avoidance than expanding my comfort zone, though I guess it amounts to much the same thing.
I get sick of this "step out of your comfort zone" meme that so many people seem to accept and bandy around uncritically, because most memes seem to be only half true, and I'm usually already aware of the ideas they express. And the comfort one comes over as rather absurd because I'm hardly ever really comfortable to begin with. Not that I never accept anything that might be somewhat painful. If I think it might be worth it, I'll give it a fair hearing and sometimes I go ahead and give it a whirl. I think the meme is aimed at people who are very comfortable but very bored, and that's not me.