Here's how it works: Say you make $50,000 a year for your full-time, 40-hour-a-week job. Calculate your monthly income after taxes: $3,500, more or less. That makes your hourly wage a little less than $22.

Next, add up all the work-related expenses you have. That includes the obvious things like office attire, commuting costs, work lunches, and dry cleaning, but also the less obvious costs that come from being tied up at work all day: daycare, housecleaning, and/or the self-care activities that help you de-stress after work.

After that, add up all the hours you spend on work when you're not at work. Commute time? Write it down. Answering emails after-hours? That too. Even the time you need to unwind when you get home counts — after all, if you weren't working, you wouldn't need to unwind.

Finally, crunch the numbers. Subtract your monthly work-related expenses from your monthly wages, and add your non-work work hours to your actual work hours. Then divide your "real" wages by your "real" work hours. Let's say you, hypothetical $50K-a-year worker, spend $1,500 a month on work-related expenses and 40 hours of work-related time outside of work. That makes your "real" hourly wage $10.

Ouch, right? Well, it's not all bad. Knowing that number could be the key to getting your spending under control.

If your "real" hourly wage is $10, that means that every $10 you spend is an hour of "life energy" — that is, it's one more hour you have to work at the end of your career to achieve financial independence. A $40 food delivery when you have groceries in the fridge? Four hours. A $100 new-clothes haul when everything in your closet still fits? 10 hours off your golden years. A $15 Uber ride when the bus is 10 minutes away? 90 minutes you'll never get back.

That's not to say every splurge isn't worth it: If you make a careful consideration and really decide it makes your life better, more power to you. But a lot of splurges don't fall into that category, and they take money away from more worthwhile pursuits that will make a real difference in your quality of life. Research shows, for example, that you're happier spending money on experiences than on things. How much faster could you save up for a Caribbean vacation without your morning latte eating up $5 — that is, a half hour of your life — every day?

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There are many more smart money lessons in "Your Money or Your Life," and we recommend checking it out. If you use that link to purchase, Curiosity will get a share of the sale.