Complacency

I'd say complacency is a danger to health! When you feel that you love the status quo, you might have fallen into the trap of complacency. When you like the situation as it is, you might rest too well such that any possibility to improve is obscure and you'll lose the notion of living to the challenge. At the end, your thoughts might have withered away.

Complacency kills! It kills your brain cell and might sway you from making improvements to your personal and/or working life. Keeping yourself on the tip of the toe once in a while is good. It keeps your brain working and ensures that you'd have enough brain cells working to prevent old age mental problem from setting in too early. Hahaha... but the root benefit is to ensure that we makes our own lives a better one each day by not being complacent. Feeling challenged is good for health provided that it doesn't set into depression as well.

Balance is the key yet complacency should be entirely avoided.