Our greatest weakness lies in giving up. The most certain way to succeed is always to try just one more time.

Maturity is often more absurd than youth and very frequently is most unjust to youth.

There is no substitute for hard work.

Just because something doesn't do what you planned it to do doesn't mean it's useless.

I am not discouraged, because every wrong attempt discarded is another step forward.

We don't know one-millionth of one percent about anything.

It is astonishing what an effort it seems to be for many people to put their brains definitely and systematically to work.

One might think that the money value of an invention constitutes its reward to the man who loves his work. But speaking for myself, I can honestly say this is not so... I continue to find my greatest pleasure, and so my reward, in the work that precedes what the world calls success.

The chief function of the body is to carry the brain around

Results! Why, man, I have gotten a lot of results. I know several thousand things that won't work.