"When you reach the end of your rope,  tie a knot in it and hang on."

-- Franklin D. Roosevelt

Great quote, here's another good one Roosevelt often used!t

"Take a method and try it. If it fails, admit it frankly, and try another. But by all means, try something."

Franklin D. Roosevelt

Almost identical!

That one is awesome too! 

"But man is not made for defeat. A man can be destroyed but not defeated."

-- Ernest Hemingway

American novelist, short-story writer, journalist, and sportsman. His economical and understated style -- which he termed the iceberg theory -- had a strong influence on 20th-century fiction, 

Those who panic will soon be under enemy control are sure overpowered by the opponent.