The ability to visualize a desired outcome is built into your brain, and your brain is designed to help you succeed in matching that picture with your performance. Da Vinci noted two types of visualization: 1) Post imagining – the imagining things that are past; 2)Pre imagining – the imagining of thing that are to be.
Keep your visualization positive. Many people practice unconscious negative visualization, more commonly known as worry. Although the ability to picture what might go wrong is essential to intelligent planning, be careful to avoid fixating on images of failure, disaster, and catastrophe. Instead, visualize your positive response to any challenge.
From How to think like Leonardo da Vinci, by Michael J. Gelb, published by Delacorte Press, 1998.