Several

Ran across some great quotes (and individuals) on Jonathan Stark's web site. Below are some of my favorites:

In times of change, the learners will inherit the world and the learned will find themselves beautifully equipped to deal with a world that no longer exists. - Eric Hoffer

Act as if what you do makes a difference. It does. - William James

There are no secrets to success. It is the result of preparation, hard work, learning from failure - Colin Powell [I continually encounter folks who put in the hard work, but lacking in either preparation or, more importantly, learning from failure... and I'm not innocent either. -jr]

Why do you wake up in the morning and do things? If you can't answer that, you might as well end it now. - Peter Baer

The measure of success is not whether you have a tough problem to deal with, but whether it's the same problem you had last year - John Foster Dulles

A problem well stated is a problem half solved. - Charles F. Kettering

A witty saying proves nothing. - Voltaire

Security is mostly superstition. It doesn't exist in nature. Life is a great adventure or it is nothing. - Helen Keller

I do not know with what weapons World War III will be fought, but World War IV will be fought with sticks and stones. - Albert Einstein

Every man takes the limits of his own field of vision for the limits of the world. - Arthur Schopenhauer

Sometimes you get the best light from a burning bridge. - Don Henley

There is no security on this earth, there is only opportunity. - General Douglas MacArthur

Learn from the mistakes of others. You can’t live long enough to make them all yourself. - Eleanor Roosevelt

Try not to become a man of success but rather to become a man of value. - Albert Einstein

Happiness depends upon ourselves. - Aristotle

In preparing for battle I have always found that plans are useless, but planning is indispensable. - Dwight D. Eisenhower

Always do right. This will gratify some people and astonish the rest. - Mark Twain

It is the mark of an educated mind to be able to entertain a thought without accepting it. - Aristotle

Do what you feel in your heart to be right - for you’ll be criticized anyway. You’ll be damned if you do, and damned if you don’t. - Eleanor Roosevelt