Every action needs to be prompted by a motive.

Make your work to be in keeping with your purpose.

Tears come from the heart and not from the brain.

There is no object so large but that at a great distance from the eye it does not appear smaller than a smaller object near.

You do ill if you praise, but worse if you censure, what you do not understand.

A well-spent day brings happy sleep.

Nothing can be loved or hated unless it is first understood.

Iron rusts from disuse, stagnant water loses its purity, and in cold weather becomes frozen; even so does inaction sap the vigors of the mind.

He who truly knows has no occasion to shout.

Beyond a doubt truth bears the same relation to falsehood as light to darkness.

All our knowledge has its origin in our perceptions.

When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return.

The knowledge of all things is possible.

Poor is the pupil who does not surpass his master.

Why does the eye see more clearly when asleep than the imagination when awake?

The noblest pleasure is the joy of understanding.

Realize that everything connects to everything else.

Obstacles cannot crush me; every obstacle yields to stern resolve.

Life is pretty simple: You do some stuff. Most fails. Some works. You do more of what works. If it works big, others quickly copy it. Then you do something else. The trick is the doing something else.