The decision

This chapter asks you to decide something. It comes late because I wanted the reasons in place first. If you'd begun here, the rule below would have felt like being told to stop caring, and it would have lasted a week.

The decision is this. Each old mistake gets one write-up. After that, I don't go back in.

Here's how to put it into practice.

Take the list from chapter 1 and add to it if more events have come to mind. Most people have between three and eight that come round regularly.

Begin with the smallest. Do its write-up this week. Do one a week after that, and leave the largest until you've had some practice.

Wherever the fifth heading names something to be done, give it a date and do it. If you've been putting off an apology for seven years, expect to want to put it off for another week. Send it anyway. It will be shorter and easier than the replays made it seem.

When an event comes back, use the three parts from chapter 13. Name it, remind yourself of its status, and turn your attention outward.

Then there are new mistakes, because you'll go on making them. The rule for a fresh one is different, since a fresh mistake does need thinking about. Give it two days. In those two days do whatever needs doing, which may mean apologising or fixing something or owning up. If it's still coming round after that, do a write-up within the week. The aim is that nothing new joins the rotation. Without this, today's blunder could become the thing you'll be replaying eleven years from now.

Plans in the form "when this happens, then I'll do that" are well supported by research. Peter Gollwitzer and Paschal Sheeran pooled 94 tests and found they made people a good deal more likely to follow through. Here are three, and you can change the wording to suit yourself.

When an old scene turns up, then I'll say its name and "that's been written up".

When I notice I'm already halfway through a replay, then I'll finish the sentence I'm on, say "written up", and look at what my hands are doing.

When I make a new mistake that stings, then I'll do what needs doing within two days and write it up within the week.

The second of those matters, because you often won't catch a replay at the start. You'll find yourself in the corridor already. That's fine. Leaving halfway through counts, and so does leaving just before the ending.

Here's what to expect, and I'll be careful because I can't promise an outcome. In the first weeks the scenes will keep arriving about as often as before. What should change first is how long you stay. A ten-minute replay becomes two minutes and then twenty seconds, and eventually the scene is something that crosses your mind without your going in. Over a few months, I'd expect the arrivals themselves to thin out for events that have been written up, and faster for ones where you've also mended something. Some will keep visiting for years, the large ones especially. A scene that visits briefly is something you can live with.

You'll have lapses. Some evening you'll be tired or low, and you'll spend forty minutes in the corridor as thoroughly as ever. That proves nothing about you or the method. Eleven years of habit doesn't vanish because you've read a book. Notice what set it off, since tiredness, drink and a bad day at work are the usual causes. Then carry on. You don't need to write anything up again. Nothing new happened.

Lastly, there are times when more than a book is needed. Please talk to a GP, or refer yourself to NHS talking therapies if you're in England, if any of these applies.

• You've had weeks of low mood, loss of interest, poor sleep or hopelessness. The NHS describes depression as symptoms that persist for weeks or months and interfere with work, social life and family life.
• The event was traumatic and returns as flashbacks, nightmares or vivid images.
• The thoughts are about harm you fear you've caused or might cause, and you're checking, confessing or mentally cancelling them out.
• The replaying takes up hours of most days despite your best efforts.
• You're having thoughts of harming yourself. Get help the same day, through NHS 111, an urgent GP appointment, or 999 in an emergency.

It may help to know that therapists treat this habit directly. Edward Watkins and colleagues have developed a form of cognitive behavioural therapy aimed specifically at rumination. It shares some ideas with this book, such as the shift from abstract "why" thinking to concrete thinking. In a trial with 42 people whose depression hadn't responded to medication, adding this therapy to their usual care improved their symptoms and remission rates, and the improvement went along with a reduction in rumination. It was a small trial and had no comparison therapy, as the authors say themselves. But it shows that the habit is known to clinicians and that it can be worked on with them.