Out of moderation a pure happiness springs.

You must be either the servant or the master, the hammer or the anvil.

If you have a great work in your head, nothing else thrives near it; all other thoughts are repelled, and the pleasure of life itself is for the time lost.

We must always change, renew, rejuvenate ourselves; otherwise, we harden.

Enthusiasm is of the greatest value, so long as we are not carried away by it.

The artist may be well advised to keep his work to himself till it is completed, because no one can readily help him or advise him with it... but the scientist is wiser not to withhold a single finding or a single conjecture from publicity.

Certain faults are necessary for the existence of the individual. We would resent it if old friends were to get rid of certain peculiarities.