If mental health has become a reactionary concept, much like the notion of public health in the age of the COVID-19 pandemic, then how can critical theory best elaborate a concern for well-being which includes both a psychic and social dimension? This article proposes the concept of existential health to grasp the salubrious zest for life that has been extinguished from social life since March 2020, due to rolling lockdowns and the rise of totalitarian impulses within the medical-industrial complex. It draws on the relational art practice of Lygia Clark along with developments in the psychedelic treatment of addiction to articulate a vision of existential health in an age of mental illness that is irreducible to the specialised domain of psychologists signified by the 'mental' in mental health.