On Anger, Book 3, Section 8 — In Plain English

Seneca — The Senator

Here's another point: when you spend time with calm people, you improve in two ways. First, their example shows you how to be better. Second, you don't find reasons to get angry, so you don't practice that bad habit. This means you should avoid people who you know will make you angry. You ask who these people are? Many different types will set you off in their own ways. A proud person will offend you with contempt. A talkative person will abuse you with words. A rude person will insult you. A spiteful person will hurt you with malice. A quarrelsome person will pick fights. A braggart will annoy you with lies and boasting. You won't be able to stand being feared by a suspicious person, defeated by a stubborn person, or looked down on by someone who thinks they're refined. Choose people who are straightforward, good-natured, and steady. They won't provoke your anger, and they'll put up with it when it does flare up. People who are flexible, polite, and smooth will help even more — as long as they don't flatter you. Too much flattery irritates people with bad tempers.

Seneca — The Senator Original

We must add to this, that the man who lives with quiet people is not only improved by their example, but also by the fact that he finds no reason for anger and does not practise his vice: it will, therefore, be his duty to avoid all those who he knows will excite his anger. You ask, who these are: many will bring about the same thing by various means; a proud man will offend you by his disdain, a talkative man by his abuse, an impudent man by his insults, a spiteful man by his malice, a quarrelsome man by his wrangling, a braggart and liar by his vain-gloriousness: you will not endure to be feared by a suspicious man, conquered by an obstinate one, or scorned by an ultra-refined one: Choose straightforward, good-natured, steady people, who will not provoke your wrath, and will bear with it. Those whose dispositions are yielding, polite and suave, will be of even greater service, provided they do not flatter, for excessive obsequiousness irritates bad-tempered men.