If you own a horse and a lance, every now and then you ought to go find a windmill.--John Haaren 

If you want to see something done, just tell some human beings it can't be done. Make it known that it's impossible to fly to the moon, or run 100 meters in 9.9 seconds, or solve Fermat's Last Theorem. Remind the world that no one has ever hit 62 home runs in a season or stuffed 18 people into a Volkswagen. Dangle the undoable in front of the world. Then, consider it done.--Merrill Lynch advertisement

If you're successful in what you do over a period of time, you'll start approaching records, but that's not what you're playing for. You're playing to challenge and be challenged.--Lou Brock

It's lack of faith that makes people afraid of meeting challenges, and I believe in myself.--Muhammad Ali

I've learned that you'll never be disappointed if you always keep an eye on uncharted territory, where you'll be challenged and growing and having fun.--Kirstie Alley

The key to life is accepting challenges. Once someone stops doing this, he's dead.--Bette Davis

Life's challenges are not supposed to paralyze you, they're supposed to help you discover who you are.--Bernice Johnson Reagon