Q:

What does "the best of us" in "the best of us must sometimes eat our words" mean?

"I seem to remember telling you both that I would have to expel you if you broke any more school rules," said Dumbledore.
Ron opened his mouth in horror.
"Which goes to show you that the best of us must sometimes eat our words," Dumbledore went on, smiling. "You will both receive Special Awards for Services to the School and...two hundred points apiece for Gryffindor."
Harry potter and the chamber of secrets

I don't exactly understand "the best of us" here. What does it mean? 

A:

Even those of us who rarely make mistakes [the best of us] must sometimes admit we have made one.
The best of us refers to the members of a group who excel in some way that is pertinent to the group's identity, focus, or sense of purpose and duty. The group can be a small one or it can include everybody.

Every runner on their team  runs a four-minute mile. Even the best of
  us cannot do it in less than 4 minutes 15 seconds. 
We have all been climbing high mountains for many years, but even the best of us need to use bottled oxygen near the summit.
We all seek to remain civil when discussing important matters with others who do not share our opinions, but even the best of us sometimes lose control and say things we later regret.

