"That's just how I am"
"I've got a temper. Always have. My dad was the same, and his dad before him." People say this in different tones. Some say it with a shrug, some with a bit of pride, and a good many with something nearer to despair.
Of all the beliefs in this book, this one has the strongest hold, because it comes with a lifetime of evidence. You've been this way for as long as you can remember. You've tried to change and gone back to it. When the moment comes, it doesn't feel like a choice. It feels like a wave that goes through you, and afterwards you can hardly believe what you said. "I just saw red." "I lost it." The language describes something that happened to you.
I accept part of this. People do differ in temperament, and the differences show up early. Some babies startle easily and howl loudly, and some of those babies grow into adults who feel everything at high volume. If that's you, you'll probably always get angry more quickly and more strongly than your placid brother-in-law. I'm not going to argue with your nervous system.
But temperament governs how fast and how strongly the feeling arrives. It doesn't dictate what you do next, and you can find the proof in your own week.
Go back to the end of the last chapter. You didn't shout at your boss. You were just as angry, perhaps angrier. The feeling was there at full strength, your heart was going, and you kept your voice level and said you'd look into it. You've likely done the same with a police officer, a customer, a doctor or your child's head teacher.
There's an even smaller example, which most people recognise with a wince. You're in the middle of a blazing row at home and your phone rings. It's a colleague, or a neighbour. You pick up and say "Hi, no, not at all, it's a good time" in a perfectly pleasant voice. Then you hang up and carry on with the row.
I'm not raising this to catch you out. It's the most hopeful fact in this book. It means the control you think you don't have is control you use daily. Something in you weighs the situation in a fraction of a second and works out whether an outburst here would be too costly. With the boss the answer is yes, and the outburst doesn't happen. At home the answer is no, because the people there have always forgiven you, and it does.
So "I lost control" is closer to "I was somewhere that control didn't seem required." It's uncomfortable to admit. It's also good news, because building a skill from nothing is hard and extending one you already have is much easier. You don't need to become a different person. The task is to move the people at home onto the list that your boss is already on.
I don't mean they should get the tight smile the boss gets. That's the clamping down from chapter 4, and it's part of the load you carry home. What you're borrowing is the pause, the fraction of a second in which you didn't let the heat speak. At home the pause comes with something the boss never gets, which is you coming back later with the point.
Now the family part. If you grew up in a house where disagreements were handled by shouting, you learned that this is how disagreement works, in the same way that you learned your accent. You may also have learned that the angriest person in the room wins, and that the only alternative to being that person was being the frightened one. It was a sensible lesson for a child in that house to draw. It explains a lot, and what you were taught as a child isn't your fault. It also means that what you inherited was mostly a method, which you can replace. You've probably noticed that you now sound like the parent you swore you'd never resemble. That tends to happen when you've only ever seen one way of doing things, so the book will show you another.
One more mechanism keeps "that's just how I am" in place, and it's the shame. After an outburst you feel awful about yourself. The feeling that you're a bad person is heavy and tense to carry, and it makes you touchier, quicker to hear criticism in a neutral remark. A touchy, tense person is nearer to the next outburst. That loop is my reading. The research behind it is more modest, and finds that people who are prone to shame also tend to be more irritable and quicker to blame others. Contempt for yourself feels like taking the problem seriously. In practice it feeds the problem. You can hold yourself fully responsible for what you did and still treat yourself as someone who can learn. That's how you'd treat anyone else you were trying to help.
One caveat, and I mean it. Some things do reduce a person's control in ways that no change of belief will mend. They include a head injury, dementia, some mental health conditions, certain medications, and heavy use of alcohol or drugs. If your temper has changed sharply or recently, or the rages come from nowhere and feel unlike you, see a doctor before you take it for a habit. If you take prescribed medication and suspect it's involved, raise it with whoever prescribed it, and don't stop taking it on your own.