Sentence:  We can repay the debt which we owe to our God, to our dead, and to our children only by work — by ceaseless devotion to the responsibilities which lie ahead of us. If I could give you a single <WSD>watchword</WSD> for the coming months, that word is: work, work, and more work. 
Meaning of the word marked with <WSD> tags:  A word used as a motto, as expressive of a principle, belief(,) or rule of action; a rallying cry.