Marcus Aurelius was absolutely right, the key to a happy life lies in your own mindset and attitude towards life, you don't need great wealth or luxuries to be happy, everything is within you, cultivating a positive and grateful thinking will allow you to appreciate the little things in life, find beauty in the simple and value personal relationships, also, having an attitude of acceptance and adaptability will allow you to face challenges with resilience and overcome them, so, don't underestimate the power of your mind and how it can influence your own happiness.
The happy life you long for is in your hands!