Every plan you have rests on a sentence nobody wrote down, and you usually meet it on the day it stops being true.
Choose plans that are in force today, not wishes: one that runs for a quarter, one for a year or two, one for a decade, such as a home, a career, a pension or your children's schooling. Write each in a single line.
Example. Follow one person through the five steps: a parent in their forties, with a job, two children and a mortgage. They pick the Q4 workload and family calendar, the children's schooling in the town where they live, and the house with its mortgage.
include one plan that other people depend on. Its assumptions are usually the quietest.
choosing three work plans because they come with a spreadsheet. Home, family and health plans hold more hidden assumptions, because nobody opens a spreadsheet for them.
For each plan, finish the sentence "This plan works as long as..." three times, fast. Typical endings: "my income arrives on time", "my town stays what it is", "my insurance still covers it", "the lights stay on", "the country stays at peace", "my children stay on their path at school", "nobody at home gets seriously ill".
Tick every kind of continuity that at least one of your plans leans on.
Then circle the ending you have never said out loud. That is the assumption. It has been true for so long that it looks like the ground, not like a premise.
Example. For the Q4 plan the parent writes "...nobody in the house is ill for more than a few days", "...the lights stay on", "...the school calendar holds". For the house: "...the insurance still covers it". They tick Health, Energy, Insurance and School and children, and circle the first ending: nowhere in the plan is there a line for illness.
the endings that feel too obvious to write down carry the most weight.
For each circled assumption, ask: what if this stops being true, and stays that way?
Keep it at that size. A bad day, a late payment or a week of flu bends a plan, and then it comes back. A change of regime moves the baseline, and the plan was written for a world that is no longer there. Write two lines: what would still work, what would stop first, and what you would have to decide in the first month.
Example. Someone in the house is ill for three months. The income would hold for a while. The calendar would stop first, because nobody else knows the school runs. In the first month the parent would have to decide who covers what, and they have never talked about it.
stay on the plan and what it leans on. If your mind starts painting the worst case, put the pen down, breathe slowly three times and come back to the question.
turning this step into a fear exercise. If fear is what shows up, the entry Face Fears is the better place for it. Come back here afterwards.
What is holding things up today: savings, a second skill, someone who would help, some slack, a spare route? A cushion buys time while you adjust. Ask how much time, and what you are doing with it.
Then take the plan where the gap between the assumption and the cushion is widest, and add one margin at the exact place the assumption sits. A budget line. A second option you have really looked into. A conversation. A skill you start this month.
Example. Three months of savings and a neighbour who might do the school runs: the cushion buys about a quarter, if the neighbour knows. The margin is two weeks of slack kept in December, and one page, shared with the neighbour and the other parent, listing who covers what.
a backup plan for every assumption. That is a second plan with its own hidden assumptions. One margin, where the plan is weakest, does more.
Write one sentence with a date: "On this date, I will check whether [the assumption] still holds, by looking at [one thing]." Pick something you will come across anyway: a number, a letter from an insurer, a conversation, a calendar.
Example. "On 1 December, I will check that the two weeks of slack are still in the calendar and the page is still current, by opening the shared calendar."
Once the assumption is named and one margin is in place, the natural next step is the entry A Plan That Expects to Be Wrong, which turns the plan into tasks, milestones and indicators.
Which assumption did you hesitate to write down, and what does that tell you about its weight?
Which of your plans would come through a bad month, and which would need rewriting if the baseline moved?
What is your cushion today, and how much time does it give you?
Who else stands on the same assumption, and have you ever said it out loud to them?
Revisit this at the start of each quarter, or the day a shock lands in someone else's life and you recognise your own plan in it.
Only what you wrote, nothing else on this page. It stays in your browser until you download it, nothing is sent anywhere.
A home and a town. A mortgage, a commute, an insurance renewal. The plan assumes the place and its cover stay what they are today.
A job and its field. Your income, your role and your sector have been steady for years. The plan assumes the next ten years look like the last ten.
The background you never planned. Everything this month assumes the lights come on and the country stays at peace. No plan mentions it, and every plan needs it.
Source Draws on assumption-based planning (James A. Dewar and colleagues, RAND), the Stoic practice of premeditatio malorum and Glenn Albrecht's concept of solastalgia. Adapted by Mat Dufour.