Sanity (noun)

1. The state of being in possession of a rational and healthy mind; the state of being sane.
2. The state of having a sound and healthy mind; not affected by a disorder of the mind.
3. The state of having a sound judgement, reasonable and rational.

Origin:

From middle english sanite, from old french sanité, from latin sanitas ("health, soundness"), from sanus ("healthy, sound").

Examples:

1. He clung to his sanity during the traumatic experience.
2. Lack of sleep can affect your sanity.
3. She was pushed to the brink of insanity, but her family helped her regain her sanity.
4. He questioned his own sanity after the accident.
5. The company's financial situation is questionable, but the board is holding on to their sanity.