It is the custom of the Samurai to always keep a sword close at hand, and be ready for battle, even to the extend of having a wooden sword or a sword without blade with him when he bathes. Likewise, it should be the custom of the artist to always have a pen or brush close at hand and be ready to paint.
Jacobo Pontormo was a Florentine master who painted anxious figures. He anticipated expressionism but was out of his time and other painters considered him a weirdo. The last 10 years of his life he worked on a single painting and refused to show it to anyone.
His withdrawn personality was similar to Michelangelo but very different from Leonardo. Amongst the great masters Leonardo da Vinci was the most sociable.
Libido is important but sometimes nightmares come from the dark, and fears inherited from the primitive jungle; They also are important.
Back in the 15th century, Albert Dürer visited Italy to study the human figure. He had to do that because people back home in Nuremberg were very prudish and he could never see them naked. This limited his study of human anatomy. Thus, it was necessary to go to Venice where he could see naked pictures (there was no Internet in the 15th century) and study the masters.
Dürer departed, but his friends cautioned him to never accept food or drink from the hands of the Italian painters. "They will try to poison you," his friends said, "to eliminate the competition!"
Sequential Art and Character Design
Leonardo and Michelangelo lived in the same century, but Leonardo was 30 years older, and they were enemies. Michelangelo for example wanted the sculpture of David to be placed in direct sunlight. Leonardo said that it must be placed inside a niche painted black, to show the figure more clearly.