I love a good quote...

You have to exclude everything purposeless and random from the sequence of your thoughts, but especially and above all anything prompted by idle curiosity or ill will. You must get into the habit of restricting your thoughts to those that are such that if you were suddenly asked, “What are you thinking?” you could answer, frankly and without hesitation, “X” or “Y,” and it would immediately be clear from your reply that all your thoughts are guileless and kindly, the thoughts of a sociable creature who disdains pleasurable or any kind of self-indulgent fantasies and is untouched by rivalry, malice, suspicion, or anything else that one would blush to admit one had in mind.
- Marcus Aurelius