In Jack Schwager’s New Market Wizards, William Eckhardt said that one mistake traders make is putting too much importance on any single trade. His suggestion was to remember that any one trade is just a small part of the bigger picture and needs to be treated dispassionately. When the individual trade becomes too important, we tend to do things to make the trade work, for example we take profits too quickly or we let losses go in hopes of a return to profitability.