Ignorance is the night of the mind, but a night without moon or star.
The demands that a great man makes are on himself; those of a petty man are upon others.
Listen widely to remove your doubts and be careful when speaking about the rest and your mistakes will be few.
Study as if you have not reached your goal - hold it as if you were afraid of losing what you have.
If a man in the morning hear the right way, he may die in the evening without regret.
The gem cannot be polished without friction nor man without trials.