5 classic but costly stock market clangers to avoid!

Our writer hopes avoiding this handful of common stock market pitfalls can improve his long-term investment returns and financial health.

The content of this article was relevant at the time of publishing. Circumstances change continuously and caution should therefore be exercised when relying upon any content contained within this article.

Bus waiting in front of the London Stock Exchange on a sunny day.

Image source: Getty Images

You’re reading a free article with opinions that may differ from The Motley Fool’s Premium Investing Services. Become a Motley Fool member today to get instant access to our top analyst recommendations, in-depth research, investing resources, and more. Learn More.

Investors have been making the same stock market mistakes for decades. Here’s a handful of errors I try to avoid!

1. Becoming emotionally attached

A share is a stake in a business. Buying or selling one therefore ought to be a rational decision.

Becoming emotionally attached to a particular position, for example because it was the first share one ever owned, can be a financially costly mistake.

2. Ignoring inconvenient signs

A common form of what psychologists call ‘cognitive dissonance’ is a confirmation bias. In everyday life, we have all experienced this when someone says “you only hear what you want to hear!”

This is dangerously common in investing too.

Take my shareholding in boohoo. Since I bought it around a year ago, the shares have continued to fall. With each piece of news, I wonder whether the worst is yet over – or still to come. Having spent money on boohoo shares, I have a natural instinct to hope for the best. But hope is not an investing strategy.

Ignoring signs about the likely valuation of a share just because they do not fit with one’s investment thesis is a mistake.

3. Too much of a good thing

As an investor, I find it a helpful discipline to identify what I think is my single best idea at any one time.

So, if I came into a windfall tomorrow and wanted to invest it, would I put it straight into my current best idea? Not necessarily. In the stock market, certainly, one can have too much of what seems like a good thing. Even the best run company can stumble, sometimes dramatically and without prior warning.

Lacking sufficient diversification is a classic investing mistake. When it costs, it can cost a lot.

4. Skipping the complex stuff

Some companies use complicated language, unusual financial metrics or opaque accounting techniques.

There are various reasons why a firm may employ such jargon or methodology. But as an investor, what matters to me is whether I can confidently value a business. If not, I cannot judge whether its shares offer me good value.

So when faced with complex corporate information, I normally do one of two things.

Either I take that as a red flag in itself and stop researching the firm, or else I dig in to learn more. Simply skipping complex parts of a company’s reports and stock market announcements because I do not understand them is a recipe for financial disaster!

5. Ignoring personal experience

Personal experience can add useful context on top of what a company reports to the stock market.

For example, one reason I continue to hold J D Wetherspoon shares despite their weak performance is because every time I go into a Spoons pub, it is heaving. Yes, the business faces ongoing challenges with inflation. But my personal observation makes me think it still has the foundations of a successful company.

However, what if a company seems to be doing well, but my personal experience is at odds with that? I would not ignore my personal experience. I would do more research to understand whether it might be part of a wider issue that could affect the investment case for a company.

C Ruane has positions in Boohoo Group Plc and J D Wetherspoon Plc. The Motley Fool UK has recommended Boohoo Group Plc. Views expressed on the companies mentioned in this article are those of the writer and therefore may differ from the official recommendations we make in our subscription services such as Share Advisor, Hidden Winners and Pro. Here at The Motley Fool we believe that considering a diverse range of insights makes us better investors.

More on Investing Articles

Warren Buffett at a Berkshire Hathaway AGM
Investing Articles

Can someone invest like Warren Buffett with a spare £500?

Christopher Ruane explains why an investor without the resources of billionaire Warren Buffett could still learn from his stock market…

Read more »

Investing Articles

Can these 2 incredible FTSE 250 dividend stocks fly even higher in 2026?

Mark Hartley examines the potential in two FTSE 250 shares that have had an excellent year and considers what 2026…

Read more »

Thoughtful man using his phone while riding on a train and looking through the window
Investing Articles

Is 45 too late to start investing?

Investing at different life stages can come with its own challenges -- and rewards. Our writer considers why a 45-year-old…

Read more »

Hand of person putting wood cube block with word VALUE on wooden table
Investing Articles

UK shares look cheap — but the market might be about to take notice

UK shares have traded at a persistent discount to their US counterparts. This can create huge opportunities, but investors need…

Read more »

Investing Articles

This FTSE 100 growth machine is showing positive signs for a 2026 recovery

FTSE 100 distributor Bunzl is already the second-largest holding in Stephen Wright’s Stocks and Shares ISA. What should his next…

Read more »

Investing Articles

I asked ChatGPT for the best FTSE 100 stocks to buy for passive income in 2026 and it said…

Paul Summers wanted to learn which dividend stocks an AI bot thinks might be worth buying for 2026. Its response…

Read more »

ISA Individual Savings Account
Investing Articles

Stop missing out! A Stocks and Shares ISA could help you retire early

Investors who don't use a Stocks and Shares ISA get all the risks that come with investing but with less…

Read more »

Investing Articles

Will Greggs shares crash again in 2026?

After a horrible 2025, Paul Summers takes a look at whether Greggs shares could sink even further in price next…

Read more »