When someone acts badly toward you or speaks badly of you, remember
that he does or says it in the belief that it is appropriate for
him to do so. Accordingly he cannot follow what appears to you but
only what appears to him, so that if things appear badly to him, he
is harmed in as much as he has been deceived. For if someone thinks
that a true conjunctive proposition is false, the conjunction is
not harmed but rather the one who is deceived. Starting from these
considerations you will be gentle with the person who abuses you.
For you must say on each occasion, “That's how it seemed to him.”