"One of the reasons why men stop running is that they lose their belief in future development. Without a training diary,a runner cannot see the pattern of training that preceded his own best performances and his own best seasons. Nor can he see the differences that led to poor performances and poor seasons.The diary keeps track of the quality and quantity of training and allows one to plan on which of these should be emphasized depending on event and time to train. Evaluations,predictions,comparisons, and future planning can be made with greater accuracy and reliability as a result of information accurately recorded in a diary. The benefits available are well worth the relatively small effort involved in the daily upkeep of a diary."
Another reason people stop running is because of repeated injuries. A running log or diary has the potential to help us avoid injuries and poor performances.