Answer:
A lot of the anxiety that comes from leaving your comfort zone is due to uncomfortable levels of uncertainty. ... The more afraid we are, the smaller our comfort zone becomes and the more difficult it is to break out of it. Familiarity is comfortable and enjoyable, so it's no real surprise that new things get our guard up, so When in your comfort zone, your brain doesn’t want anything to change. Your needs are met, you have zero stress, and your brain recognizes that the body is surviving. It’s a recipe for steady performance.
Your brain especially doesn’t like change. It requires so much energy for day-to-day activity that it doesn’t want to give extra resources to the attention required to do new thingsGetting out of your comfort zone from time to time creates just enough good stress to ramp up your focus, creativity, pace, and drive, and it helps you respond to life stress when unexpected things happen.