I think a man's duty is to find out where the truth is, or if he cannot, at least to take the best possible human doctrine and the hardest to disprove, and to ride on this like a raft over the waters of life.
Let others laugh when you sacrifice desire to duty, if they will. You have time and eternity to rejoice in.
Duty is not collective; it is personal.
You cannot hope to build a better world without improving the individuals. To that end each of us must work for his own improvement, and at the same time share a general responsibility for all humanity, our particular duty being to aid those to whom we think we can be most useful.
It is humankind's duty to respect all life, not only animals have feelings but even also trees and plants.
Michael de Montaigne
Don't waste life in doubts and fears; spend yourself on the work before you, well assured that the right performance of this hour's duties will be the best preparation for the hours and ages that will follow it.