Note to Much Ado About Nothing, 1.3.4: "therefore the sadness is without limit"

A little later in the scene we learn that Don John has opposed his half-brother, Don Pedro, in battle. Don John lost the battle, but Don Pedro has forgiven him rather than punishing him. Don John could have been executed or imprisoned, so it seems that his "sadness" should have a limit, since he could have suffered much worse than he has. However, his feeling is that just because he has no good reason for his bitter mood, it has no limits. He is the sort of villain who always feels disrespected and who is always looking for ways to get revenge on a world which he believes has mistreated him.