Running for example. It's hard to do. It takes preparation. You loose your breath. You might get sore. Well, it was like that at some point (or still is). Your brain put that thing outside the comfort zone. But running is good for you. After a week a running you start to feel better over...

Things there are easy to do. Part of it because we got used to them, like driving. You don't really think about them before actually doing them.

The comfort zone is not good in telling you what you should do or not do. Nor is it just these two categories. Stabbing yourself with a pencil is outside the comfort zone and bad for you. Walking is inside your comfort zone (running is not) but that doesn't mean you shouldn't go ...

The comfort zone makes it hard and uncomfortable to do stuff outside that zone, but it also gets smaller if we don't push it. Things that were right on the edge (but still inside) of the comfort zone suddenly take a lot of effort to do.