I never once failed at making a light bulb. I just found out 99 ways not to make one.
The stomach is the only part of man which can be fully satisfied. The yearning of man's brain for new knowledge and experience and for more pleasant and comfortable surroundings never can be completely met. It is an appetite which cannot be appeased.
Seeming to do is not doing.
Our greatest weakness lies in giving up.
Success is based on imagination plus ambition and the will to work.
There is no substitute for hard work.