On Anger, Book 3, Section 28 — In Plain English

Seneca — The Senator

Anger hurts many people, making them weak or broken, even when they attack someone who doesn't fight back. And no creature is so helpless that you can destroy it without any risk to yourself. Sometimes sorrow or bad luck makes the weakest person as dangerous as the strongest. Here's something else to think about: most things that make us angry are insults, not actual harm. There's a big difference between someone actively blocking what you want and simply not helping you get it. There's a difference between someone stealing from you and just not giving you something. Yet we react the same way whether someone takes something from us or refuses to give it to us. We get equally mad whether someone crushes our hopes or just delays them. We don't care if they meant to hurt us or were just helping themselves. We don't care if they acted out of love for someone else or hatred for us.

Seneca — The Senator Original

Anger makes many men cripples, or invalids, even when it meets with an unresisting victim: and besides this, no creature is so weak that it can be destroyed without any danger to its destroyer: sometimes grief, sometimes chance, puts the weakest on a level with the strongest. What shall we say of the fact that the greater part of the things which enrage us are insults, not injuries? It makes a great difference whether a man thwarts my wishes or merely fails to carry them out, whether he robs me or does not give me anything: yet we count it all the same whether a man takes anything from us or refuses to give anything to us, whether he extinguishes our hope or defers it, whether his object be to hinder us or to help himself, whether he acts out of love for some one or out of hatred for us.