The 30-something’s guide to the actual maths of starting over

On the calculation most people never write down and why the real numbers are almost always better than the anxiety ones.

Hi, I’m Katie! Welcome to The Multiple Lives Theory. This is a space for anyone rewriting the rules of modern work, embracing a nonlinear career, and actively designing a life of creative freedom outside the standard 9-5 ladder.

The maths that stops you was never actually calculated

There’s a kind of maths that runs in the background of every career-change conversation, and it almost never gets written down.

It goes: I’m thirty-one. If I start something now, I won’t have real traction for two years. The people already doing this have a ten-year head start. By the time I have what they have, I’ll be forty-five.

I know this maths intimately, because I ran it, in various configurations, for about three years before I stopped. It was always available when I needed a reason to wait.

The calculation that runs in the background

What I never did, for an embarrassingly long time, was check it. I treated it as a fact about the world rather than a sum I could actually sit down and do. It hummed away, generating reasons to wait until the conditions were better, until I was more prepared, until the risk felt smaller and it never once resolved, because I never once wrote it down.

Anxiety maths vs actual maths

Anxiety maths is felt, not computed. It runs in the background, uses no real numbers, and exists mainly to justify waiting. Actual maths is written down. It uses your real figures, includes the cost of staying, and uncomfortably tends to produce a different answer.

When I finally ran the actual version, I found the anxiety calculation had three structural errors in it. Not emotional errors.

The maths was simply wrong.

Where the anxiety maths goes wrong

• The compound-interest assumption. Anxiety maths measures the gap between where you are and where someone established is now, then projects how long to “catch up.” But catching up assumes the same trajectory. The person ten years ahead is optimising within a lane; you’re still in the steep part of your own curve, where everything you learn changes how you learn. The gap is real. The projection is wrong.

• The opportunity-cost miscalculation. Anxiety maths adds up what you’d give up, salary, stability, status — but almost never subtracts what staying costs: the skill atrophy, the network you’re not building, the options quietly closing while you wait. Staying has a price too. The sum should include it.

• The “is it too late” binary. This frames the question as yes-or-no, and conceals a premise — that there’s a correct time you may have missed. But almost nothing worth doing has a correct time. It has a range. And within that range, earlier beats later, so the honest answer to “is it too late” is almost always: later than if you’d started when you first thought about it, and earlier than if you wait.

• What I actually did (the numbers)
  I’m sharing these because most people don’t, and the opacity feeds the anxiety. I had roughly seven months of living expenses saved. I had two small clients I’d been working with part-time for about four months, generating around a third of my old salary. I had a plan to reach full income replacement in twelve months, and I was wrong about the timeline altogether. It took about fifteen in total.

The gap was uncomfortable and manageable. The numbers weren’t special. They weren’t a set of circumstances that made the decision obviously sensible. They were enough (barely) to make it survivable. And survivable, it turns out, is the relevant threshold. Not safe. Not certain. Just survivable.

Why nobody writes it down

Writing the maths down makes it real in both directions. It makes the risk real. The exact number of months you could last, the exact income you need to hit. But it also makes the survivability real, and the survivability, looked at with actual numbers rather than anxiety, is usually far less catastrophic than the background hum suggests.

How to run the actual maths

1. Write the number down. A vague calculation can’t resolve. A written one can.

2. Include what staying costs. Not just the salary you’d keep but the options you’d lose.

3. Find the floor: survivable, not safe. You’re not solving for certainty. You’re solving for “can I get through the gap.”

4. Treat “too late” as a premise, not a fact. Ask what correct-time it’s secretly assuming, then check whether that time exists.

5. Decide on the real number, not the feeling. They’re almost always different.

What surprised me

When I finally ran my own numbers, the thing that surprised me was how much energy I’d been spending just maintaining the anxiety version.
The vague, unexamined calculation takes constant work. It hums and never settles. Writing it down made it less consuming, even when the answer was harder than I’d hoped. A real number, however uncomfortable, has an edge.

And you can work with an edge.

— Katie

What calculation have you been running in your head that you’ve never actually written down? Reply and tell me, or if you’ve done the maths, I want to hear what it said.

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More from Multiple Lives Theory:

→ the reinvention story we’re not telling — on why moving comes before clarity

→ the relief you’re not allowed to feel when the job ends — on the honest feeling underneath the leap

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Multiple Lives Theory is a weekly essay on nonlinear careers, reinvention and the emotional reality of changing your life. Sundays and Thursdays.