Expect obstacles
Principle 4 from the Enchiridion
Expecting some friction makes it easier to keep your judgment when the day gets messy. Most plans come with delays, mistakes, or difficult people.
Original Passage
When you are going about any action, remind yourself what nature the action is. If you are going to bathe, picture to yourself the things which usually happen in the bath: some people splash the water, some push, some use abusive language, and others steal. Thus you will more safely go about this action if you say to yourself, "I will now go bathe, and keep my own mind in a state conformable to nature." And in the same manner with regard to every other action. For thus, if any hindrance arises in bathing, you will have it ready to say, "It was not only to bathe that I desired, but to keep my mind in a state conformable to nature; and I will not keep it if I am bothered at things that happen."
Modern Interpretation
Epictetus asks us to preparing your mind before you begin. Most activities come with annoyances you can see coming: delays, interruptions, mistakes, and difficult people. It is easy to get upset not only because something went wrong, but because we assumed it should all go smoothly.
Expecting some friction means you are less surprised when it arrives. You may still plan carefully and prefer an easy day. You stop making perfect conditions a requirement for acting with good judgment.
In Practice
A common version of this is easy to recognize. You leave for work and traffic is awful. Someone cuts you off, the train is late, and your mood is wrecked before the workday even begins.
Before leaving, you could remind yourself that commuting often includes delays and inconsiderate people. When the delay happens, it is still inconvenient. You just do not have to add an hour of anger to it.
Reflection Question
What could reasonably go wrong in your next routine activity? How would you like to respond if it does?