Here is one of my favorite quotations that is relevant to your theme.

This is the true joy in life,

the being used for a purpose

recognized by yourself as a mighty one;

the being thoroughly worn out

before you are thrown on the scrap heap;

the being a force of Nature

instead of a feverish selfish little clod of ailments and grievances

complaining that the world will not devote itself

to making you happy.

George Bernard Shaw

From the dedication to Man And Superman