Plenty of get-rich schemes promise to make people millions. Some are day-trading programs with lofty testimonials: “I bought this software, and turned $10,000 into $1 million in just four years. You could do it too.” Others might sell real estate investment schemes. “I paid just $100 a month for this real estate investment guide. I went from zero to hero and retired in five years.”

There’s no shortage of smoke and mirror schemes that promise quick riches. I suggest you ignore them all. Instead, follow an evidence-based plan. It won’t make you wealthy fast. But it should lead to riches, instead of heartache and loss.

The first step is to track what you spend. Plenty of spending apps are available online. My wife and I use Pocket Expense. Some other popular apps include Goodbudget and Mint. Plenty of people say you should create a weekly budget. But I’m not one of them. Your spending can fluctuate wildly, month-to-month. If you take a big trip, or have a surprise home repair, it might blow your budget and make you feel like a failure. To me, budgets are like diets. Sometimes they work…but they usually don’t.

Researchers from Kaiser Permanente Center for Health Research followed more than 1,700 dieters over a six-month period. The biggest single predictor of whether a participant would lose weight was whether they documented their food intake. It was a better indicator than exercise, age and body mass index.

When we document what we eat and spend, it increases accountability. This helps us eat better and spend less money. When we spend less, we have more money to invest. I recommend a portfolio of low-cost index funds. Over long time periods, a portfolio of index funds should increase your wealth.

Imagine somebody saving $150 a week from 1985-2019. If they invested 70 percent in a U.S. stock index and 30 percent in a U.S. bond market index, they would have about $1.2 million today.

You might wonder how to come up with $150 a week. Let your expense tracker help. After you’ve been tracking your expenses for a couple of months, examine what you’re spending money on. You’ll see pie charts representing each of your spending categories. Some of your expenses will look frivolous. You’ll be spending money on certain things that don’t give you a lot of value. Others will be the opposite.

For example, my wife and I spent $150 a week on massages from 2003-2014. Over those 11 years, they cost $79,200. We were also investing money from 2003-2014. Our portfolio of index funds averaged a compound annual return of 8.34 percent.

If we had invested that money, instead of spending it on massages, it would have grown to $132,221 by 2014. I was 44-years old that year. If we had continued to let that money grow (without adding another penny) it would have likely grown to a small fortune. If it continued to average 8.34 percent per year, it would be worth about $710,993 by the time I reached 65 years of age.

I’m not saying, however, that I wasted that money. We loved those massages. When we looked at our expenses, we chose not to give them up. But we found other ways to cut our spending. If you track your spending, you’ll likely do the same. When doing so, you’ll find money to invest that you didn’t know you had.

That’s what happens when we track what we spend. Every financial decision has an opportunity cost. In other words, it’s the long-term benefit of making one decision over another, like investing money that we would have otherwise spent. Several decisions, for example, have long-term opportunity costs of at least a million dollars. They include smoking a pack of cigarettes a day, leasing cars instead of buying used, eating lunch at a café every workday, instead of bringing sandwiches from home.

Nobody should tell you what to cut back on. Let your personal value system decide that instead. There might not be a foolproof way to quickly build wealth. But an evidence-based long-term plan will give you a fighting chance.

Andrew Hallam is a Digital Nomad. He’s the author of the bestseller, Millionaire Teacherand Millionaire Expat: How To Build Wealth Living Overseas