Solitude matters, and for some people it is the air that they breathe.

Cain’s line argues that solitude is not a luxury or a sign of social failure, but a basic psychological need—especially for introverts and other highly sensitive temperaments. By likening solitude to “the air that they breathe,” she frames time alone as essential for emotional regulation, creativity, and clear thinking, not merely a preference. The quote also implicitly critiques cultures and workplaces that equate constant sociability with health or competence. Its significance lies in validating inner-directed lives and insisting that well-being can require protected quiet, boundaries, and freedom from perpetual stimulation.