When it comes to building wealth, the stock market can be your best friend -- and you yourself can be your own worst enemy. Our own irrational behaviors are what can destroy a lot of the gains we had or had hoped for in a variety of ways.

Here's a look at some common mistakes related to timing -- and how to avoid them.

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Let's start with a biggie: market timing. It's when investors try to jump into the market at what they think is a great time and/or when they exit, fearing a crash. A 2025 report from the folks at Vanguard offered multiple reasons why we should think twice before market timing. For instance:

"Bull market surges have been longer and stronger than the bear markets that preceded them." So, getting out of the market at a downswing can mean missing some or much of a big upward run.

"Timing the market is futile; the best and worst trading days often happen close together." If you sell on one day, the market might surge over the next few days, leaving you on the sidelines.

See how Larry Fink, CEO of BlackRock (NYSE: BLK), the world's largest money manager, tackled the topic in his recent annual letter to shareholders:

But over time, staying invested has mattered far more than getting the timing right. Over the past two decades, every dollar invested in the S&P 500 grew more than eightfold. Miss just the ten best days, and you would have earned less than half. And some of the market's strongest days came amid the most unsettling headlines.

For best results, remember that the market will correct or crash on occasion, and there will be recessions, and if you just take deep breaths during these events and stay invested, you'll likely do better than if you tried to guess what the market will do next.

A similar situation in which our irrational behavior can lose us a lot of money is when we act emotionally, either buying into stocks out of greed or selling them in a panic.

The fear of missing out, or FOMO, applies not just to watching TV shows you don't enjoy because everyone else is doing so but also to investing, such as when people jump into cryptocurrencies without understanding them.

Growth stocks can be exciting and can help your portfolio grow faster, but remember that they can fall harder than other stocks during a market downturn. Ideally, buy into them when they're undervalued, fairly valued, or not too overvalued.

Similarly, many investors bail out when the market crashes. That's the worst time to bail out, as it locks in lower gains or even losses. As long as you have faith that the companies you own will do well in the long run, consider just hanging on. Many have made millions by just holding on to great stocks through ups and downs.

Warren Buffett, arguably one of the most rational investors ever, has advised: "Investors should remember that excitement and expenses are their enemies. And if they insist on trying to time their participation in equities, they should try to be fearful when others are greedy and greedy when others are fearful."

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Selena Maranjian has no position in any of the stocks mentioned. The Motley Fool recommends BlackRock. The Motley Fool has a disclosure policy.

The Investor Behavior That Destroys More Wealth Than Any Market Crash was originally published by The Motley Fool