Embrace the faith that every challenge surmounted by your energy; every problem solved by your wisdom; every soul stirred by your passion; and every barrier to justice brought down by your determination will ennoble your life, inspire others, serve your country, and explode outward the boundaries of what is achievable on this earth.--Madeleine Albright 

The great and invigorating influences in American life have been the unorthodox: the people who challenge an existing institution or way of life or say and do things that make people think.--Justice William O. Douglas 

The great crises of life are not, I think, necessarily those which are in themselves the hardest to bear, but those for which we are least prepared.--Mary Adams 

The greatest challenge we face as human beings is acting on what we know. We don’t lack for knowing, we lack for doing.--Mark Sanborn ( Up, Down, or Sideways) 

I have always grown from my problems and challenges, from the things that don't work out, that's when I've really learned.--Carol Burnett 

I leave you love. I leave you hope. I leave you the challenge of developing confidence in one another. I leave you respect for the use of power. I leave you faith.--Mary McLeod Bethune 

I often feel that our greatest individual challenge is to close the gap between our unflattering self-concepts and the truth of our magnificence. To see ourselves through the eyes of those who love us.--Jeff Brown (Ascending with Both Feet on the Ground: Words to Awaken Your Heart) 

If the processes don't transfer, they cannot even be called thinking. They can be called learning, memory, or habit, but not thinking. The purpose of a course on thinking is to enhance student's abilities to face new challenges and to attack novel problems confidently, rationally and productively.--Marilyn Jager Adams 

 If you compared your troubles, or challenges, with those of others, you would surely find that there are those whose troubles make yours look like minor inconveniences.--Catherine Pulsifer
  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