Too much comfort is dangerous. Literally.
Researchers at the University of California, Berkeley, did an experiment some time ago that involved introducing an amoeba into a perfectly stress-free environment: ideal temperature, optimal concentration of moisture, constant food supply. The amoeba had an environment to which it had to make no adjustment whatsoever.
So you would guess this was one happy little amoeba. Whatever it is that gives amoebas ulcers and high blood pressure was gone.
Yet, oddly enough, it died.
Apparently there is something about all living creatures, even amoebas, that demands challenge. We require change, adaptation and challenge the way we require food and air. Comfort alone will kill us.
(John Ortberg, If You Want to Walk on Water, You've Got to Get Out of the Boat)