Knowledge is knowing that we cannot know.

Experience without theory is blind, but theory without experience is mere intellectual play.

Positive thinking will let you do everything better than negative thinking will.

Be miserable. Or motivate yourself. Whatever has to be done, it's always your choice.

Optimism is the faith that leads to achievement. Nothing can be done without hope and confidence.

Strong and bitter words indicate a weak cause.

Perhaps I am stronger than I think.

There is little that can withstand a man who can conquer himself.

Out of suffering have emerged the strongest souls; the most massive characters are seared with scars.

Do not let what you cannot do interfere with what you can do.

Silence is a source of great strength.

It doesn't take a lot of strength to hang on. It takes a lot of strength to let go.

No one saves us but ourselves. No one can and no one may. We ourselves must walk the path.

Strength and growth come only through continuous effort and struggle.

Success is a science; if you have the conditions, you get the result.

Pray that success will not come any faster than you are able to endure it.

Success - keeping your mind awake and your desire asleep.

Don't be afraid to give your best to what seemingly are small jobs. Every time you conquer one it makes you that much stronger. If you do the little jobs well, the big ones will tend to take care of themselves.

Never put off till tomorrow what you can do the day after tomorrow.

Success is a science; if you have the conditions, you get the result.

Think twice before you speak, because your words and influence will plant the seed of either success or failure in the mind of another.

Success is dependent on effort.

Science is the highest personification of the nation because that nation will remain the first which carries the furthest the works of thought and intelligence.

The goal of education is the advancement of knowledge and the dissemination of truth.

Always bear in mind that your own resolution to succeed is more important than any other.

The starting point of all achievement is desire.

Success is a lousy teacher. It seduces smart people into thinking they can't lose.

It is not clear that intelligence has any long-term survival value.

Intelligence is the ability to adapt to change.

It is always wise to look ahead, but difficult to look further than you can see.

Thousands of candles can be lighted from a single candle, and the life of the candle will not be shortened. Happiness never decreases by being shared.

I can accept failure, everyone fails at something. But I can't accept not trying.

All the great things are simple, and many can be expressed in a single word: freedom, justice, honor, duty, mercy, hope.

Someone told me that each equation I included in the book would halve the sales.

I have no special talent. I am only passionately curious.

The true sign of intelligence is not knowledge but imagination.

Change is the law of life. And those who look only to the past or present are certain to miss the future.

The world is the great gymnasium where we come to make ourselves strong.

Always bear in mind that your own resolution to succeed is more important than any other.

When your desires are strong enough you will appear to possess superhuman powers to achieve.

No man can succeed in a line of endeavor which he does not like.

Cherish your visions and your dreams as they are the children of your soul, the blueprints of your ultimate achievements.

The ladder of success is never crowded at the top.

The majority of men meet with failure because of their lack of persistence in creating new plans to take the place of those which fail.

Edison failed 10,000 times before he made the electric light. Do not be discouraged if you fail a few times.

Every adversity, every failure, every heartache carries with it the seed of an equal or greater benefit.

Always bear in mind that your own resolution to succeed is more important than any other.

Think twice before you speak, because your words and influence will plant the seed of either success or failure in the mind of another.

It is no use saying, 'We are doing our best.' You have got to succeed in doing what is necessary.

Success is a science; if you have the conditions, you get the result.