I've been thinking a lot about the math.
Not the feel-good math. The unforgiving kind — the math that shows up decades later and tells you what your decisions really cost. Three mistakes from my 20s have already cost me over a million dollars. One of them cost me something I'll never get back.
Here they are, in the order they hit me.
Mistake #1: Being blinded by persuasion instead of being a truth-seeker
I was 22 when I bought my first car. I absolutely shouldn't have.
It's not that I didn't understand the numbers. I did — just not in their entirety. A very convincing salesman fed me a rehearsed pitch and a few cherry-picked figures. I felt the pressure. I went with it. Months later, I realized the real cost was nothing like what he'd shown me.
That mistake cost me thousands. Compounded out through Mistake #2, it became tens of thousands.
Here's the pattern I've watched play out with so many of us in our 20s and 30s: we make poor financial decisions not because we're careless, but because we're guided by persuasion, not truth. Sales and marketing win over math. There's almost always an inner voice saying "I'm not fully sure how this works" — and we override it because the salesman sounds confident.
The worst version isn't skipping the math. It's doing incomplete math — the math the salesman wants you to do — and feeling like you did your homework.
Jeff Bezos famously banned PowerPoint at Amazon. Teams write six-page memos instead. His reasoning: presentations turn reality into a sales pitch. They highlight the exciting parts and conveniently hide the uncomfortable ones.
A car or a house deserves truth, not persuasion. The flyer persuades. Excel tells the whole truth.
My non-negotiable now: I want total math. Not half math. If the complete numbers check out, I move forward. Otherwise I walk away. Letting a good deal pass is far cheaper than getting stuck with a bad one.
Mistake #2: Not realizing money is in a lifelong relationship with time
Most people think of money in isolation — dollars, rupees, euros. That's the beginner's lens, and it quietly wastes the most important wealth-building years of your life.
Money isn't single. It's in a relationship with time. And unlike most relationships, this one you can actually count on.
In wealth-building, time does the heavy lifting — not just the amount. If you're young, your dollar amount might be small, and that's fine. You're time-wealthy. You can start building the investing muscle decades sooner, and the math gets absurd.
Picture two people, both with $1M. One is 21. The other is 42.
At first glance, they look similar — both doing well. Now zoom out. If each one parks it in the S&P 500, which historically doubles roughly every 7 years:
- At 28 / 42 → $2M vs $1M
- At 35 / 49 → $4M vs $2M
- At 42 / 56 → $8M vs $4M
- At 49 / 63 → $16M vs $8M
- At 56 / 70 → $32M vs $16M
They're not even close. And we didn't add a single penny to either starting amount.
That changes everything. The house. The vacations. The way your parents spend their final years.
So that $1,200 iPhone? For a 21-year-old, it isn't $1,200. It's roughly a $40,000 decision pulled from your 60-year-old self. The iPhone today might be a car later.
I'm not telling you to stop buying things you want. The goal is to live well — present and future. Buy them. Just know their complete price.
Don't envy the 50-year-old in the nice car. Their dollar currency is there. Their time currency is gone.
Mistake #3: Treating financial literacy as a hobby
This is the one I'm still coping with.
For most of my teens and 20s, I treated personal finance as a "topic of interest." Something I liked reading about. Watching videos on. That's not enough. Not even close.
My MBA broke that for me forever. I sat in Excel for four days straight — Thursday to Sunday night, fourteen hours a day — building financial models and slowly realizing how wrong my mental model had been.
The conclusion: my net worth could have been 2.8 to 3.1 times what it already was, with zero lifestyle changes. None. And I wasn't broke. I'd bought my first stock at 18 and become a millionaire in my 20s, so I'd done fine by most standards. I still paid the ultimate price for treating financial literacy like a hobby.
Through my 20s, I worked hard. Earned more. Invested decently. Climbed.
The motivation underneath all of it was giving my parents an unbelievable old age. They'd sacrificed so much for me. I had it all mapped out — the first-class flights, the experiences, all of it. I wanted them to feel every bit of it.
Just after I turned 30, my dad suddenly got sick.
We spent months in hospitals. A few months later, he died.
That's it. Bye bye.
People say life is delicate. I always agreed. But when it actually happens to you, it changes things. A train came out of nowhere and broke me into pieces.
Today, my capacity to give my parents the experiences I'd dreamt up is the highest it's ever been. The money is there. It doesn't matter. He's not.
The Two Golden Principles of Financial Literacy
Don't make my mistake of thinking of financial literacy as just a topic you're interested in.
If you take one thing from this, take this: it's not about becoming financially literate. It's about when you become financially literate. And it doesn't have to be from me — pick whichever voice feels right to you.
Personal finance respects exactly two things:
- A small number of high-quality decisions
- Early action
Both are about time. Both compound. Neither can be bought back.
This is the reason I turned down a seven-figure offer from Facebook and started writing about this instead. The money here was never about the money. It never will be.
Build your financial wellbeing now — so the people whose lives you'd improve with it are still around to enjoy it.