DUTY

In a single sentence Emerson crystallizes the faith that nothing is
impossible to those whose guide is duty. His words, though spoken
primarily of youth, apply to the whole of human life.   

"So nigh is grandeur to our dust,  
 So near is God to man, 
 When duty whispers low,
 _Thou must_,  
  The youth replies, _I can_."

_Ralph Waldo Emerson._