W. Clement Stone was just 3 when his father died, leaving nothing but gambling debts and a widow and son in poverty. At age 6, he was selling newspapers on the street to help support his family. He thought of himself as a “self-builder” and ultimately became a pioneer in personal development, publishing Success Unlimited in 1954, the predecessor to SUCCESS magazine.

Stone documented his philosophies in the personal development classic he co-authored with Napoleon Hill in 1960, Success Through a Positive Mental Attitude. Here are some of his core principles:

Seek clarity of purpose.
“All personal achievement starts in the mind of the individual. Your personal achievement starts in your mind. The first step is to know exactly what your problem, goal or desire is.”

Develop a positive attitude.
“There is little difference in people, but that little difference makes a big difference. The little difference is attitude. The big difference is whether it is positive or negative.”

Embrace failure.
“With a positive mental attitude failure is a learning experience, a rung on the ladder, a plateau at which to get your thoughts in order and prepare to try again.”

Look for the opportunity.
“Every great man, every successful man, no matter what the field of endeavor, has known the magic that lies in these words: every adversity has the seed of an equivalent or greater benefit.”

Know the secret to happiness.
“To be happy, make other people happy.”