comfort zone

noun2

1. •
   The range of temperature, humidity, and other environmental factors that people or other organisms require in order to be physiologically unstressed.

   • The child who swings between extremes has trouble finding the comfort zone—the area in which her body is comfortable, efficient, and alert. — 2014
2. •
   The range of circumstances in which a person feels relaxed or able to cope.

   • The demanding interview panel took him well out of his comfort zone.