No matter what a brilliant career or what great achievements a person has, he is left with only himself in the end. One’s own body and one’s own soul are the only thing a person can truly have.
Some people live their lives as a money-making machine, and the whole purpose of their life is to earn more money than they can spend. In the early stages, when they move from poverty to wealth, they can feel some happiness, but later on, it just becomes a mechanical movement, and they can no longer feel any happiness, just a dull and number feeling, and they can only go on working till they die.
Some people live a completely altruistic life: they sacrifice their own happiness and comfort entirely to raise children or care about their elders, but they never achieve happiness for themselves, they only work hard, turning their existence into a long penance, becoming pure ascetics.
Some people spend their lives in labour, just like a screw, meticulously doing their assigned task, only playing the role of a screw, and not enjoying the fruits of their hard labour. This kind of existence may very well be that of a screw, with hardly anything organic, hardly any breath of life to it.
The truly happy life is one continually aware of itself, one that continuously appreciates love and beauty, one continuously returning and reflecting on itself. And in this process of awareness and reflection, it will see what joy it has and hasn’t experience, and to what extent.