Mental health encompasses emotional, psychological, and social well-being, influencing cognition, perception, and behavior. According to World Health Organization (WHO), it is a "state of well-being in which the individual realizes his or her abilities, can cope with the normal stresses of life, can work productively and fruitfully, and can contribute to his or her community". It likewise determines how an individual handles stress, interpersonal relationships, and decision-making. Mental health includes subjective well-being, perceived self-efficacy, autonomy, competence, intergenerational dependence, and self-actualization of one's intellectual and emotional potential, among others. From the perspectives of positive psychology or holism, mental health may include an individual's ability to enjoy life and to create a balance between life activities and efforts to achieve psychological resilience. Cultural differences, personal philosophy, subjective assessments, and competing professional theories all affect how one defines "mental health". Some early signs related to mental health difficulties are sleep irritation, lack of energy, lack of appetite, thinking of harming oneself or others, self-isolating, and frequently zoning out.

Well-being, or wellbeing, also known as wellness, prudential value, prosperity or quality of life, is what is intrinsically valuable relative to someone. So the well-being of a person is what is ultimately good for this person, what is in the self-interest of this person. Well-being can refer to both positive and negative well-being. In its positive sense, it is sometimes contrasted with ill-being as its opposite. The term "subjective well-being" denotes how people experience and evaluate their lives, usually measured in relation to self-reported well-being obtained through questionnaires.