Tone and Diction

I am reading Watership Down by Richard Adams and I have finished the first nine chapters of the novel. The main character Hazel has been introduced, along with his band of compatriots: Fiver, Bigwig, Blackberry, Dandelion, Pipkin, Buckthorn, Silver, Hawkbit, Acorn, and Speedwell. These eleven rabbits have left their warren because of a vision of Fiver's that "something terrible is coming". So far the story's tone and setting is very dark and sad but at the same time optimistic. At one point Dandelion is asked to tell a story of El-ahrairah, the Prince of Rabbits, and it follows this exact same point. 

"El-ahrairah, your people cannot rule the world, for I will not have it so. All the world will be your enemy, Prince with a Thousand Enemies, and whenever they catch you, they will kill you. But first they must catch you, digger, listener, runner, prince with the swift warning. Be cunning and full of tricks and your people shall never be destroyed."

The thought first imposed in this quote is awful. "All the world will be your enemy", is a horrible thing to think; yet at the same time, "Be cunning and full of tricks and your people shall never be destroyed", seems so wonderful. Rabbits are fast and tricky so this doesn't seem bad at all. 

Be exactly what a rabbit is and survive? 

Absolutely!