3 costly investing mistakes to avoid

To become better investors, we first need to recognise where we’re going wrong. Paul Summers offers up three investing mistakes of his own.

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.

Hispanic man using laptop in home office and drinking coffee

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.

Becoming better at anything usually involves needing to reflect on our errors. Stock picking (and holding) is no different. Here are three investing mistakes that have held me back over the years and how I’ve tried to overcome them. 

Mistake #1: Having too little/too much patience

Unless I’m queueing for petrol, I like to think of myself as a patient soul. However, there have been times over my investing journey where I’ve been unable to sit on my hands. This has usually involved snatching at profits ( FTSE 100 stock Halma springs to mind) or selling on a bit of temporary bad news (step forward online casino operator 888). Just to muddy the waters somewhat, I’ve also been too patient at times and waited for a recovery that never arrives. Sometimes it’s better to get out, stay out, and take the loss.

There’s no perfect solution here. However, simply getting into the habit of reflecting on exactly why I’m wanting to act/not act is a start. Keeping a journal and revisiting my reasons for buying a particular stock also helps. Has a company’s strategy changed? Is this now a better business? If yes, why sell?

Mistake #2: It’s all about the price

The ‘buy low, sell high’ mantra persists because it’s patently good advice. However, investing mistakes arise when I tend to put too much weight into categorising something as ‘cheap’ or ‘expensive’. An expensive stock becomes a bargain if the underlying business grows massively. A cheap share can become cheaper if the underlying business is failing.

Now, let’s not get silly here. I’m not suggesting a stock trading on a P/E of 20 is somehow cheaper than one trading on a P/E of 10. My point is simply to look beyond this basic metric and ask whether the price is fair relative to what I’d be getting for it.

Does the company consistently deliver great returns on capital? Is it unfairly valued compared to sub-standard rivals? Does it have the finances to withstand a stock market crash? If so, I’ve likely found a good business worth paying more for. 

Owners of Fundsmith Equity will know that Terry Smith always puts quality ahead of price when picking stocks. To date, this has enhanced rather than impeded his returns.

Mistake#3: Listening to the noise

It’s remarkably easy to assume that the more information I gather about a stock, the greater the edge I have over my peers.

This tactic isn’t necessarily irrational. Finding a promising company that’s flying under many investors’ radars can sometimes generate incredible returns. Think Argo Blockchain from December 2020 to Feburary 2021. 

That said, any information-grabbing exercise must always consider the quality of the source. Back in the day, for example, I’d pay attention to forums and social media sites like Twitter. There would be the odd useful nugget among the dross, but the signal-to-noise trade-off was invariably poor. 

These days, my approach is far more focused and reflects my limited time. My first port of call is always the London Stock Exchange’s news page. I’ll also listen to podcasts or audiobooks from/about proven investors (William Green’s ‘Richer, Wiser, Happier’ is highly recommended).

Again, this won’t guarantee great returns. Even the best are still susceptible to investing mistakes. Nevertheless, standing on the shoulders of identifiable giants rather than unverifiable online personas sounds far less risky.

Paul Summers owns shares in Fundsmith Equity. The Motley Fool UK has recommended Halma. 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

Young Caucasian man making doubtful face at camera
Dividend Shares

Will the Diageo share price crash again in 2026?

The Diageo share price has crashed 35.6% over one year, making it one of the FTSE 100's worst performers in…

Read more »

Investing Articles

Is Alphabet still one of the best shares to buy heading into 2026?

The best time to buy shares is when other investors are seeing risks. Is that the case with Google’s parent…

Read more »

Investing Articles

Could the Barclays share price be the FTSE 100’s big winner in 2026?

With OpenAI and SpaceX considering listing on the stock market, could investment banking revenues push the Barclays share price higher…

Read more »

Investing Articles

Will the Nvidia share price crash in 2026? Here are the risks investors can’t ignore

Is Nvidia’s share price in danger in 2026? Stephen Wright outlines the risks – and why some might not be…

Read more »

Middle-aged white man pulling an aggrieved face while looking at a screen
Growth Shares

I asked ChatGPT how much £10,000 invested in Lloyds shares 5 years ago is worth today? But it wasn’t very helpful…

Although often impressive, artificial intelligence has its flaws. James Beard found this out when he used it to try and…

Read more »

Portrait of pensive bearded senior looking on screen of laptop sitting at table with coffee cup.
Investing Articles

Did ChatGPT give me the best FTSE stocks to buy 1 year ago?

ChatGPT can do lots of great stuff, but is it actually any good at identifying winning stocks from the FTSE…

Read more »

Surprised Black girl holding teddy bear toy on Christmas
Investing Articles

Who will be next year’s FTSE 100 Christmas cracker?

As we approach Christmas 2025, our writer identifies the FTSE 100’s star performer this year. But who will be number…

Read more »

Businessman with tablet, waiting at the train station platform
Investing Articles

I asked ChatGPT for an 8%-yielding passive income portfolio of dividend shares and it said…

Mark Hartley tested artificial intelligence to see if it understood how to build an income portfolio from dividend shares. He…

Read more »