According to Fidelity’s research, 401(k) millionaires achieve their success through consistent saving and long-term commitment to their plans. They typically save 15% or more of their income, often including employer matches, and start contributing as early as possible. Fidelity found that most of these millionaires stay invested for 20 years or longer, allowing compound growth to multiply their returns. They avoid panic-selling during market downturns and remain disciplined through economic cycles. Their portfolios are usually diversified, with a heavy focus on low-cost index funds and target-date funds. Many also increase their contributions over time as their income grows, maximizing the benefits of tax-deferred investing. Ultimately, Fidelity’s data shows that 401(k) millionaires are built through patience, consistency, and a long-term mindset—not by chasing quick wins.