Lifestyle, work, and relationships are some of the main ways we define ourselves and find meaning. The best argument for regular exercise (to me) is that it’s the most reliable way to feel good about yourself. We were evolved to break a sweat everyday.
Working out once probably gives the approximate relief that a dose of pharmaceutical ketamine does, which is probably the most effective chemical intervention. Unlike ketamine, however, more benefits accumulate the more regularly you do it. No one’s ever proud of all the ketamine muscles they’ve built up.