Challenges strengthen your soul. Sergei Bodrov Jr.
I think we're going to the moon because it's in the nature of the human being to face challenges. It's by the nature of his deep inner soul... we're required to do these things just as salmon swim upstream. Neil Armstrong
The manager accepts the status quo; the leader challenges it. Warren Bennis
Truth lives, in fact, for the most part on a credit system. Our thoughts and beliefs pass, so long as nothing challenges them, just as bank-notes pass so long as nobody refuses them. William James
Life is a lot more fun if you treat its challenges in creative ways. Bill Gates
The most stupid chicken always challenges the wildcat. Bantu Proverb