Excellent performers judge themselves differently than most people do. They're more specific, just as they are when they set goals and strategies. Average performers are content to tell themselves that they did great or poorly or okay.
By contrast, the best performers judge themselves against a standard that's relevant for what they're trying to achieve. Sometimes they compare their performance with their own personal best; sometimes they compare it with the performance of competitors they're facing or expect to face; sometimes they compare it with the best known performance by anyone in the field.
Any of those can make sense; the key, as in all deliberate practice, is to choose a comparison that stretches you just beyond your current limits. Research confirms what common sense tells us, that too high a standard is discouraging and not very instructive, while too low a standard produces no advancement.
Geoff Colvin, Talent is Overrated