The joy of the mind is the measure of its strength.
Do not dwell in the past, do not dream of the future, concentrate the mind on the present moment.
If you talk to a man in a language he understands, that goes to his head. If you talk to him in his language, that goes to his heart.
You can do anything, but not everything.
Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away.