All sciences are vain and full of errors that are not born of Experience, the mother of all Knowledge.
Leonardo Da Vinci
He who can copy can do.
I have wasted my hours.
I thought I was learning to live; I was only learning to die.
He who loves practice without theory is like the sailor who boards ship without a rudder and compass and never knows where he may cast.
The painter will produce pictures of little merit if he takes the works of others as his standard.