One of the most useful ideas in the book is Mat’s Spending Personality Indicator (MSPI), which is a simple but powerful tool to help you figure out why you spend the way you do.

It’s not about good or bad habits. It’s about understanding yourself, because no budgeting app or advice column works unless you know why you buy things in the first place.

The MSPI is designed to help people figure out not just where their money is going, but why they keep spending in ways that don’t always make sense to them after the money’s been and gone.
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What Is the MSPI?
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The MSPI is a practical framework to help you work out your spending personality. It’s inspired by popular personality tests like Myers-Briggs, but tailored for spending behaviour not psychology jargon.

Mat designed MSPI around three key ‘dimensions’:
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1. Understanding – Do you actually know your financial situation? Are you regularly checking your balance or are you mostly guessing or even avoiding knowing at all?
   
   
2. Receptiveness – Do you tend to just accept prices, contracts, and renewals—or do you push back, negotiate, and question things?
   
   
3. Impulsiveness – Do you plan your purchases, or are you the person who walks into a shop for one thing and leaves with five?
   
   

These three factors combine to give you one of 8 Spending Personality Types. 

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The 8 Spending Personalities: Which One Are You?
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Here’s a breakdown of the MSPI types:

1 The Nightmare
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If you’re a Nightmare, you don’t know where your money’s going, you never challenge costs, and you tend to spend impulsively. It’s a tough combo because it creates a downward spiral—overspending leads to anxiety, which leads to ignoring the problem, which leads to more overspending. The good news? You can change this. Awareness is the first step.

2 The Pleaser
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Pleasers hate confrontation. You probably let contracts auto-renew, never haggle, and might even find it hard to ask someone to pay you back. You may not spend wildly, but you get financially taken advantage of because you’re too nice. Building confidence in negotiating—even just one bill at a time—can transform your finances.

3 The Ostrich
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You know you should be changing things but don’t. You might be someone who loudly announces they don’t “do” finances, even though deep down you’re worried about it. This combination is tricky because it mixes denial (that ostrich head stuck in the ground) with defiance. Start small—one financial task at a time—and get the momentum going.

4 The Hoarder
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Ever found yourself bulk buying things you don’t really need, convinced you’re saving money? Hoarders do exactly that. They confuse quantity with value and often overbuy. It’s thoughtful spending applied in the wrong places. To improve, focus on asking: Do I actually need this?

5 The Coveter
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This one hits close to home for many of us. Coveters know better, but can’t resist shiny things. Whether it’s the latest phone, trendy trainers, or luxury holidays, you’ve got financial knowledge but give in to social pressure and lifestyle creep. Start by introducing delays to purchases or setting “fun budgets” so splurges are intentional.

6 The Classic
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Congratulations—you’re The Classic. You’re aware of your finances, you make considered decisions, but you don’t rock the boat too much. You’re generally doing fine, but you could take things further by being a bit more defiant: asking for better deals, challenging renewals, and fine-tuning your financial setup.

7  The Hustler
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Hustlers love a bargain and hate getting ripped off, but they’re also prone to big impulse buys - especially on things they don’t need. You’ve got sharp instincts but sometimes go overboard. Use that rebellious streak to protect your money, not just to chase dopamine hits from purchases.

8 The Zen Master
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This is where we’d all like to be: you know your money, you ask the right questions, you don’t waste cash, and you don’t cave to pressure. If you’re here then keep going. Just don’t get complacent. Even Zen Masters can slip back without regular check-ins.

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Why Does It Matter?
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Knowing your MSPI type gives you a huge advantage over your unconscious spending patterns. It gives shape to the vague feeling of “Why do I keep doing that?” and turns it into something you can work on (especially if you read the advice in Mat’s book).
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For example:
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• If you’re impulsive:  set a 24-hour rule before making non-essential purchases.
  
  
• If you’re overly accepting: commit to cancelling or renegotiating at least one bad-value subscription this month.
  
  
• If you’re clueless about your finances: start with just checking your account balances regularly, or use tools like HyperJar to visually organise your spending.
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Most personal finance advice ignores psychology. But according to Mat:

“You can know all the financial tricks in the world, but if you don’t deal with the emotional stuff underneath, you’ll still overspend.”

The Goal Is Progress, Not Perfection
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Mat’s message throughout the book is clear: this isn’t about shaming yourself or aiming for financial perfection. It’s about understanding who you are, spotting the weak points in your habits, and nudging yourself toward smarter decisions.

“It’s just about doing smarter habits every day, consistently,” he says. “The gains feel invisible at first, but over time, they add up to something powerful.”

When you start to see spending as a personal habit, rather than just numbers on a spreadsheet, it becomes easier to make changes that last. And as Mat points out; good money habits, like good health habits, pay off not just in your wallet but in your wellbeing too.

He adds: “Don’t try to be perfect. Play the long game. It’s about tiny shifts, from a small deficit to a small surplus. Over time, that can make a huge difference without making your life miserable.”

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Intrigued? You can buy Mat’s book via Amazon and Waterstones, and from all good book shops.

And of course, you can start exploring and managing your financial behaviours with the HyperJar app. Download it now if you’re not already a convert.

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