You need to avoid certain things in your train of thought: everything random, everything irrelevant. And certainly everything self-important or malicious. You need to get used to winnowing your thoughts, so that if someone says, “What are you thinking about?” you can respond at once (and truthfully) that you are thinking this or thinking that. And it would be obvious at once from your answer that your thoughts were straightforward and considerate ones.

~ Marcus Aurelius