The 1 Investing Habit That Separates Stock Market Millionaires From Everyone Else

Becoming a millionaire by investing in stocks isn’t easy, but with enough time and one habit in particular, on paper it’s a very attainable task. Research by Fidelity indicates that there were 769,000 401(k) millionaires at the end of June 2026, who as a group have been investing for an average of 25 years.

Those investors have a range of different backgrounds, money stories, and lives. Yet, unlike many of those who are not yet millionaires, they likely share one investing habit in particular, and probably almost without exception.

Consistency has many forms, and most are indispensable

People who have made millions investing in stocks have the habit of consistency. Consistency can mean many things, but I’m willing to bet that nearly all of these millionaire investors got a lot of mileage out of consistently investing in an index fund, like the Vanguard S&P 500 ETF (VOO +0.30%).

That exchange-traded fund (ETF) tracks the S&P 500 and has an expense ratio of 0.03%. The fund itself launched in 2010, but buying the index was possible long before that. Buying the index is one of the most reliable ways to get a good return on capital over long periods of time. The S&P 500 compounded at a pace of about 10% annually from 1928 through 2025 when dividends were reinvested.

That long-term performance opens up a lot of doors for those with time.

A 25-year-old in their first real job investing $100 per week throughout their career, until age 65, would see that 10% return (on average) play out in their favor again, and again, and again. Their $208,000 in contributions across their working life would ultimately compound to reach a value of roughly $2.4 million. Moreover, building those millions really only required thinking about the investment one time, briefly, at the very start, when the investor set up an automated plan to purchase the ETF once per week.

Despite the minimal thinking required for that investment, investors would, in truth, need another kind of consistency to capture the full benefit: emotional consistency.

The S&P 500, like all markets, goes through bear phases, bull phases, crashes, and episodes of intense trading. Wanting to pause contributions during or right after a crash or a bear market is only human. But that’s actually the wrong move. The best approach is to maintain a consistent long-term view, with index fund investments made each week regardless of the market’s behavior at any given time.

To let up on the gas right when prices are lower is to let fear get in the way of consistency, and that’s something the most successful stock investors avoid if they can.

Consistent purchasing can work with individual stocks too

Index funds aren’t the only things worth buying consistently over time. Millionaire investors often consistently purchase certain high-performing blue chip stocks that have reliably stood the test of time.

For example, Costco Wholesale and Apple are the kind of durable and evergreen businesses that could be worth buying every month on a perpetual basis. Both companies have large, loyal customer bases, high brand value, and consistent earnings growth across a variety of economic environments. However, keep in mind that this habit magnifies whatever you aim it at over time. Most stocks are poor targets, as they’re not able to adapt to the ever-changing economic conditions in which they operate.

The last reason why consistency is the most important habit shared by millionaire stock investors is that consistently showing up to invest whenever you’re able will, over the long run, likely beat those who didn’t bother to show up regularly.

Even an investor with an imperfect investing schedule, not much capital, and an imperfect judgment of which assets to buy will likely beat those who invest only when they feel rich enough (and confident enough) to risk money, or only when they’re motivated by a flight of fancy. So set a schedule, ideally through automatic contributions to a 401(k) plan, lock in for the long run, and don’t give up.

Consistency is a habit that can be built, and for serious investors, it’s a must-have.