Just as courage imperils life, fear protects it.
Threats alone are the weapons of the threatened man.
Wherever good fortune enters, envy lays siege to the place and attacks it; and when it departs, sorrow and repentance remain behind.
He who walks straight rarely falls.
It is bad if you praise, and worse if you reprove a thing, I mean, if you do not understand the matter well.
It is ill to praise, and worse to reprimand in matters that you do not understand.
Taken from The Notebooks of Leonardo da Vinci edited by Jean Paul Richter, 1880.