In just four words, Marcus Aurelius captures a fundamental cure for anxiety, regret, and mental suffering. The present moment is the only time we can actually influence through our thoughts, decisions, and actions - it's where real power lies and where peace is found. Past and future exist only in our minds, often as sources of unnecessary suffering: the past breeds regret, guilt, and rumination, while the future generates anxiety, worry, and fearful speculation. By confining our attention to the present, we escape these mental prisons and engage with reality as it actually is. This isn't passive acceptance but active engagement - the present is where we can practice virtue, make meaningful choices, and experience life directly rather than through the distorting lens of memory or imagination.