The rest of your money should be invested, because both bonds and stocks have typically returned substantially more than cash equivalents like C.D.s and money market funds, he writes. And he is correct, assuming you can afford to keep your money invested over long periods and can ride out downturns. Between 1926 and 2017, according to research done by Ibbotson, part of Morningstar, an investment research and management company, large stocks returned 10.2 percent a year and government bonds provided a 5.5 percent annual return.

Second, Mr. Sethi provides solid advice on how to divide your money between stocks and bonds. If you don’t want to spend a lot of time determining your asset allocation, he suggests using target-date mutual funds, investments intended to increase assets over a fixed period of time.

The further away your goal — such as retirement — the more of your money that is invested in stocks. As your goal draws nearer, the fund automatically shifts your money into more conservative investments.

The third thing I like is his concept of “conscious spending.”

“Conscious spending isn’t about cutting your spending on everything,” he writes. “That approach wouldn’t last two days. It is quite simply about choosing the things you love enough to spend extravagantly on — and then cutting costs mercilessly on the things you don’t love.”

Mr. Sethi even suggests a budget for how this might work. You’d spend 50 to 60 percent of your take-home pay on fixed costs such as rent or mortgage, utilities and student debt.

Ten percent would go to your investments, such as your 401(k). Another 5 to 10 percent would be put aside to fund specific large purchases such as a down payment on a house. That would leave 20 to 35 percent to spend guilt-free.

Fourth, Mr. Sethi says it becomes much easier to achieve your goals if you make them extremely specific. Sure, you can simply say you want to retire with a lot of money. But it will probably be easier to remain focused on your retirement if you specify that you want to end up with, say, $1.7 million in retirement savings, in part because you want to spend two months in Tuscany every year once you stop working. (That’s my example, not Mr. Sethi’s.)