When do you hope to retire? 65? 60 if you really get frugal? Mr. Money Mustache left the working world at 30, and he wants you to, as well. The popular personal finance blogger (who only reveals that his first name is Pete) has gained a loyal following by insisting that early retirement is really pretty easy, if people only shake off their wasteful attitudes about debt and consumerism. He spoke with Vox via email about how people can amp up their saving and investing and quit their jobs a few years earlier.

DK: What's the most common mistake you see people making with their money?

MMM: You could probably sum it up as taking a very short-term view on money and life: "I have $5 in my wallet right now, so I can afford this coffee," or "I make more than $399 per month, so I can afford to borrow money for this car."

Instead, I try to get people to think of things in 10-year chunks at a minimum and then move on to a lifetime perspective. For example, spending $100 per week on restaurants equates to a $75,000 hit to your wealth every ten years, compared to keeping that money and just investing it in a conservative way.

"if you have credit card debt, you should feel like your hair is on fire"

Instead of thinking of income as a temporary stream of cash that keeps you afloat, think of every dollar as a potential permanent lifetime employee that will work for you as long as you keep and invest it. But once you spend it, that particular dollar is gone.

DK: I really appreciate that you phrase your philosophy on money in terms of happiness. What's a good way to put that into practice, though -- if i'm standing at the store and thinking, "That dress would make me happy," what can I ask myself to figure out if I really should buy it?

MMM: The first trick is to remind yourself that buying something — pretty much anything — is very unlikely to improve your long-term happiness. Science figured this out for us long ago, but not many people got the memo. Go to your junk electronics drawer and look at your old flip phones or your dusty iPad 1. Look at the clothes you've recently pruned from your closet that are now headed to the Goodwill. You traded a lot of good dollars for those, not very long ago at all. Are they still making you happy today?

Then think about what would really make you happy. For me, it was the freedom to choose how I spent my days, with no worries about money for the rest of my life. Again, every dollar that you keep for yourself will immediately start paying dividends towards this freedom. Your stress about money drops away, and you can walk away from a job or a boss you're not fond of — the options start to open up with breathtaking speed as you step away from the financial cliff.

DK: What do you and your family splurge on?

MMM: I feel that we splurge on everything. For example, we live in a house that looks like it came from the pages of a modern architecture magazine, overlooking a park and within walking distance of downtown. I have not just one car, but two of them, which we never even use because we also have six bicycles between the three of us. We also eat ridiculously fancy food at home and take some pretty exotic vacations. Everything seems really over-the-top, considering the fact that we could be just as happy with much less.

But for other people, my life might seem like the opposite of a splurge: "What? Three people live in only 1,500 square feet? Their cars are from 2005 and 1999? That sounds like a really extreme life of frugality!"

The key to all of this is to zoom out a bit and put things in perspective. Both my life and your life are ridiculously abundant and safe compared to almost every human who has ever lived before you in the history of this planet. If we can't be happy in this incredible place of privilege, we need to punch ourselves in the face and try again.

DK: How did you get started in the area of personal finance? And what informs your views here — did your parents talk money much with you growing up?

MMM: I was born as the stereotypical engineer kid, which means I was always interested in optimizing everything. Money was just one of those things.

It was only after I turned 30 and had enough money to retire from real work that I started getting these incredulous comments from friends and coworkers, like "What do you mean you are retiring? How will you get the money to pay your car loan and your mortgage? I'd be sunk within a month if I lost my job."

"[when i became a dad] i suddenly realized that the real issue is not a shortage of money but a constant shortage of time"

To me, their stories were much more amazing than my own story of early retirement. They were the same age as me or older, and had equal or higher salaries. I couldn't imagine having a shortage of money in such amazing conditions. Then I looked even higher up the income scale and found the same phenomenon. It turns out that humans are capable of blowing almost any amount of money, without realizing they are doing it.

This is what led me to start the Mr. Money Mustache blog to explain my perspective on money.

DK: My sense is that people have a better instinctual grasp of how to save than invest. Let's say someone has the cutting-back part down. Where does a beginner begin on investing?

MMM: Investing is scary until you understand how simple it is. The key for me was to recognize that stocks are not gambling instruments - they are slices of ownership in real, productive companies that will work with you for life. You eliminate all the risk by holding thousands of stocks simultaneously through a low-cost index fund.

For example, you can beat most of the world's investors by just buying and holding Vanguard's Total Stock Market Index Fund. Throw in all your paychecks, ignore the news headlines, and let the dividends reinvest for your whole working career. You'll do just fine.

Nowadays, I feel you can do slightly better by owning an even wider basket of investments — for example, Vanguard LifeStrategy growth fund or a 90-percent stock index portfolio through Betterment, which I have started an experiment with myself, documenting it on the blog.

I think of money invested in index funds as being safe, and hard at work for me. Money sitting around in cash is in danger — not working, tempting me to buy a Tesla Model S, and being eroded by inflation. So I keep all money invested.

DK: You advise people to get rid of debt emergencies. But how should someone decide how much debt is OK and what debt will be a problem?

MMM: Most people are far too complacent about debt in this country, so I try to shake up that perception a little. For example, it is considered normal to borrow money when buying a new car, when in fact it is a completely ridiculous bit of financial suicide. People accept credit card debt (and pay 20-percent interest on it) with a sigh of resignation, while continuing to do things like buy gourmet coffee or go out to dinner.

If you have credit card debt, you should feel like your hair is on fire. You shouldn't be eating anything beyond baked potatoes and tap water or doing anything besides working overtime and sleeping until you get out of that emergency. I've never been that frugal myself, but that's because I have never gotten into credit card debt.

Really, it boils down to the interest rate and the purpose of the loan. If you mortgage a home at today's rates, then live a reasonable life and invest your surplus income in retirement savings, you'll do fine: on average the house will appreciate almost as fast as the interest rate, plus it pays you "dividends" in the form of not having to rent an apartment.

But suppose you have some student loans at 6-percent interest kicking around in the background as well. They might have a low minimum monthly payment, but they are still draining your wealth at a significant rate. You need to pay those off before you go on to more frivolous spending, like regular nights out on the town or trips to the Caribbean.

You're in debt, which should be considered a problem that needs to be resolved. Otherwise, you are effectively financing everything you buy at 6 percent, instead of putting that money to work by eliminating interest costs.

"money ... is like tap water, just there in the background to meet our needs"

DK: How has having a partner -- and, I imagine more importantly, a kid — changed how you think about money?

MMM: If you and your partner share a common philosophy about what it means to live a good life, this part is easy. Back in the early 2000s, my wife and I were starting to think about having a kid or two eventually. But we realized that the demanding nature of our jobs in high-tech were not a good match for this — kids get sick and need you at home, school adjourns for three months every summer, and software projects ramp up and demand that you work late or travel occasionally. We decided that the most efficient way to handle that situation was to eliminate the need to work for money before having the first kid. So we saved and invested most of our paychecks together.

Once we retired and our boy was born [nine years ago], the thoughts about money didn't really change. Babies are much less expensive than people assume they are. But they are also much more work. Becoming a dad hit me like a freight train initially, when I suddenly realized that the real issue is not a shortage of money, but a constant shortage of time. I was incredibly thankful that I wasn't also trying to balance a full-time job in with this activity.

Money is something we don't think about at all — it is like tap water, just there in the background to meet our needs. You use whatever you need and you know it will never run out, but there's no thrill in letting it go to waste either.

For me, early retirement has never been about ceasing work or productive activity. Just breaking free of working to somebody else's agenda and schedule, or having the threat of running out of money influencing my decisions of what to work on. The good life is all about plenty of hard work doing stuff you love to do.

This interview has been edited for clarity and length.