There is scientific evidence that visualization improves performance. One study involves basketball free throws at the University of Chicago. The study first measured the free throw ability of players and divided students into three different groups. The first group was told to practice their shots one hour a day. The second group was told to stand in front of the basket and visualize taking their shots. The third group was told to ignore basketball.
After 30 days:
Physical practice only improved performance one percent higher than visualization. This proves the power that the mind has over performance and the usefulness of visualization.