"I-think-I-can, I-think-I-can." One of the classic children's stories we love is The Little Engine That Could by Watty Piper, though Watty Piper really wasn't a person, but the publishing house Platt & Munk that published a version in 1930 of The Pony Engine that originally appeared in 1910. There is an interesting history explained at Wikipedia:
The Little Engine That Could is a moralistic children's story that is used to teach children the value of optimism and hard work. In the tale, a long train must be pulled over a high mountain. Various larger engines are asked to pull the train; for various reasons they refuse. The request is sent to a small engine, who agrees to try. The engine succeeds in pulling the train over the mountain while repeating its motto: "I-think-I-can".
The tale with its easy-to-grasp moral has become a classic children's story and has been told and retold many times. The underlying theme however is the same - a stranded train is unable to find an engine willing to take it on over difficult terrain to its destination. Only the little blue engine is willing to try, and while repeating the mantra "I-think-I-can, I-think-I-can" overcomes a seemingly impossible task.