Think only what is essential

“If you seek tranquillity, do less.” Or (more accurately) do what’s essential—what the logos of a social being requires, and in the requisite way. Which brings a double satisfaction: to do less, better.
Because most of what we say and do is not essential. If you can eliminate it, you’ll have more time, and more tranquillity. Ask yourself at every moment, “Is this necessary?”
But we need to eliminate unnecessary assumptions as well. To eliminate the unnecessary actions that follow.

— Marcus Aurelius, Meditations, 4:24 (the fabulous Hays translation)

That last paragraph is where the gems hide. Pare away unnecessary activities yes. But more important: pare away unnecessary assumptions. Unnecessary thoughts. Unnecessary beliefs, theories.

Compare this to Paul Graham’s idea of keeping your identity small.

He says certain areas of human activity have no ultimate “correct” answer and no minimum barrier to entry. Any asshole is an expert on Twitter.

It is these areas (politics and religion are his examples) that infect one’s sense of self–one’s identity. And once a topic has become a part of YOU, there is no compromise or admitting of mistakes. You’re stuck.

I think what religion and politics have in common is that they become part of people’s identity, and people can never have a fruitful argument about something that’s part of their identity. By definition they’re partisan.
Which topics engage people’s identity depends on the people, not the topic. For example, a discussion about a battle that included citizens of one or more of the countries involved would probably degenerate into a political argument. But a discussion today about a battle that took place in the Bronze Age probably wouldn’t. No one would know what side to be on. So it’s not politics that’s the source of the trouble, but identity. When people say a discussion has degenerated into a religious war, what they really mean is that it has started to be driven mostly by people’s identities.

Here is his solution (emphasis added):

The most intriguing thing about this theory, if it’s right, is that it explains not merely which kinds of discussions to avoid, but how to have better ideas. If people can’t think clearly about anything that has become part of their identity, then all other things being equal, the best plan is to let as few things into your identity as possible.

Marcus Aurelius and Paul Graham probably would find common ground.

Anderson would agree, too. “Do you know what a closed mind is?” he would demand. “Uhhhhh. . . . ” would come the reply, cut of by Anderson saying “A closed mind is one so full of its own thoughts that it doesn’t have any room for new ones.”

Think only the essential thoughts. Believe only the essential beliefs. Tranquillity lives here, within and without.