Insanity is defined as a state of mind where someone is irrational, mentally ill or insane. The antonym of "in-sane" is "sane", meaning mentally stable, rational and normal. It is important for one to maintain a balance in their mental health to ensure that they can function properly in their daily lives. Some more antonyms for "in-sane" include "sensible", "logical", "coherent" and "stable". In today's world, it is vital to prioritize mental health and wellbeing as it can have a significant impact on one's personal and professional life. Being sane and mentally stable helps in making sound decisions and navigating through life's challenges with ease.