Seneca

Seneca on the duty of a man…

The duty of a man is to be useful to his fellow-men; if possible, to be useful to many of them; failing this, to be useful to a few; failing this, to be useful to his neighbours, and, failing them, to himself: for when he helps others, he advances the general interests of mankind. Just as he who makes himself a worse man does harm not only to himself but to all those to whom he might have done good if he had made himself a better one, so he who deserves well of himself does good to others by the very fact that he is preparing what will be of service to them.”