Writing in Meditations, Marcus Aurelius reminds himself that it's not external events that cause us difficulties, but the interpretation we choose to place on them.
"Choose not to be harmed— and you won’t feel harmed. Don’t feel harmed— and you haven’t been... It can ruin your life only if it ruins your character." (4.7 and 4.8)
We have our emotions, and we have our thoughts about them. We can't control the former but we can control the latter, and we need to stop them fusing with each other.
"The mind is the ruler of the soul. It should remain unstirred by agitations of the flesh— gentle and violent ones alike. Not mingling with them, but fencing itself off and keeping those feelings in their place. When they make their way into your thoughts, through the sympathetic link between mind and body, don’t try to resist the sensation. The sensation is natural. But don’t let the mind start in with judgements, calling it “good” or “bad.”" (5.26)
The only things we should label "good" or "bad" are the things in our control: our own actions.
“You take things you don’t control and define them as “good” or “bad.” And so of course when the “bad” things happen, or the “good” ones don’t, you blame the gods and feel hatred for the people responsible— or those you decide to make responsible. Much of our bad behavior stems from trying to apply those criteria. If we limited “good” and “bad” to our own actions, we’d have no call to challenge God, or to treat other people as enemies.” (6.41)
To be grateful for what we have without allowing ourselves to become dependent on those things:
“Treat what you don’t have as nonexistent. Look at what you have, the things you value most, and think of how much you’d crave them if you didn’t have them. But be careful. Don’t feel such satisfaction that you start to overvalue them— that it would upset you to lose them.” (7.27)
To trust ourselves:
“It never ceases to amaze me: we all love ourselves more than other people, but care more about their opinion than our own.” (12.4)
To be self-reliant:
"Poor: (adj.) requiring others; not having the necessities of life in one’s own possession." (4.29)
To not worry about praise...
"Beautiful things of any kind are beautiful in themselves and sufficient to themselves. Praise is extraneous. The object of praise remains what it was— no better and no worse.... Is an emerald suddenly flawed if no one admires it?" (4.20)
...or our reputation:
"Or is it your reputation that’s bothering you? But look at how soon we’re all forgotten. The abyss of endless time that swallows it all. The emptiness of all those applauding hands. The people who praise us— how capricious they are, how arbitrary. And the tiny region in which it all takes place. The whole earth a point in space— and most of it uninhabited." (4.3)
To recognise that we are not responsible for the behaviour of others:
"So other people hurt me? That’s their problem. Their character and actions are not mine." (5.25)
To not extrapolate from first impressions:
“Nothing but what you get from first impressions. That someone has insulted you, for instance. That— but not that it’s done you any harm. The fact that my son is sick— that I can see. But “that he might die of it,” no. Stick with first impressions. Don’t extrapolate. And nothing can happen to you.” (8.49)
To see no more than is actually there:
“Like seeing roasted meat and other dishes in front of you and suddenly realizing: This is a dead fish. A dead bird. A dead pig. Or that this noble vintage is grape juice, and the purple robes are sheep wool dyed with shellfish blood. Or making love— something rubbing against your penis, a brief seizure and a little cloudy liquid. Perceptions like that— latching onto things and piercing through them, so we see what they really are. That’s what we need to do all the time— all through our lives when things lay claim to our trust— to lay them bare and see how pointless they are, to strip away the legend that encrusts them.” (6.13)