About this passageThe opening of the second book, written by a Roman emperor in a private notebook he did not intend anyone to read. Long's 1862 translation keeps the archaic second person, which is worth noticing: the whole work is addressed to himself. The passage is a rehearsal performed before the day starts, and the reason it gives for not hating anyone is a claim about kinship rather than about tolerance.
Begin the morning by saying to thyself, I shall meet with the busybody, the ungrateful, arrogant, deceitful, envious, unsocial. All these things happen to them by reason of their ignorance of what is good and evil.
But I who have seen the nature of the good that it is beautiful, and of the bad that it is ugly, and the nature of him who does wrong, that it is akin to me, not only of the same blood or seed, but that it participates in the same intelligence and the same portion of the divinity, I can neither be injured by any of them, for no one can fix on me what is ugly, nor can I be angry with my kinsman, nor hate him.
For we are made for cooperation, like feet, like hands, like eyelids, like the rows of the upper and lower teeth. To act against one another then is contrary to nature; and it is acting against one another to be vexed and to turn away.
In plainer words
Start the morning by telling yourself: today I am going to run into people who are nosy, ungrateful, arrogant, dishonest, jealous and unfriendly. They are like that because they cannot tell what is actually good from what is actually bad. But I have seen it, so none of them can damage me — nobody can make me ugly — and I cannot hate a relative. We were built to work together, like two hands, like the upper and lower teeth. Being obstructive to each other is against the design. So is turning away in a huff.
A restatement in modern English, written for this collection. The passage above is the text; this is one way of putting it.