Originally Posted by WildVolley
As I understand it, shot tolerance is how many balls a player is used to/willing to hit into play before they feel they must end the point by hitting an awesome shot.
Clay court specialists, for instance, are believed to have a higher shot tolerance, and don't mind hitting 30 balls in a row to win a point. Serve and volley players tend to want to conserve energy and end the point quickly and will become very uncomfortable if pinned to the baseline and therefore, because of a lack of shot tolerance, go for a winner even if they don't have the ball they want.
IMO this is an excellent explanation.