Share your opinion and earn yourself a free Motley Fool premium report!

We are looking for Fools to join a 75 minute online independent market research forum on 15th / 16th December.

To find out more and express your interest please click here

The biggest mistake investors make, and how I avoid it

Rupert Hargreaves explains how he’s trying to avoid the biggest mistake investors can make when they start investing in the stock market.

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.

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.

The biggest mistake investors can make is buying a stock they don’t understand

I’m willing to bet every single investor has made this error at some point in their career. That includes this author. 

What a mistake to make

When I first started investing, I mistakenly thought I knew a lot about the oil and gas market. After all, I had spent hours and hours reading about the industry and studying successful companies as well as investments. 

However, I had no actual experience within the industry. I couldn’t really tell if a prospective oil well was going to be successful. Also, I couldn’t tell if a company had the resources to develop a potentially lucrative oil resource. 

Luckily, I realised I was making an error in judgement before I clocked up any severe losses, although I did end up losing money. Today, I’ve a far deeper understanding of the oil and gas sector, which I’ve been able to develop over the past decade-and-a-half. 

Unfortunately, it’s all too easy to make this mistake. All too often, investors get caught up in the story rather than keeping a cool head. When investors get caught up in the story, rather than focusing on the fundamentals, it can be easy to overlook critical factors.

This is where mistakes happen. I made the mistake of focusing on the story all too often with oil and gas companies. I failed to acknowledge the challenges many firms encounter when trying to develop oil and gas wells. 

Stick to what you know

I’m trying to avoid repeating these mistakes by sticking to the companies I know best. In many ways, this is easier said than done. I don’t think you really get to know a business until you have owned it for at least a year. Following the organisation closely during this time gives enough room to learn about the enterprise. 

Following a company closely allows me to build up an idea of what makes it tick, how it earns money, and if I really understand the enterprise. If I don’t understand the business, I’m not going to try and force it. What’s more, I don’t want to rush the process, as this could lead to mistakes. 

Of course, this is a time-consuming process and, on more than one occasion, I’ve  missed a great opportunity. But that’s the risk I’m willing to take. I’d much rather miss an opportunity to make money than jump into a company I don’t understand and lose money. 

This approach may not be suitable for all investors because it does require time and concentration. Nevertheless, I believe that by following this approach, I’ve been able to avoid repeating the mistakes I made early on in my career. 

Rupert Hargreaves has no position in any of the shares mentioned. The Motley Fool UK has no position in any of the shares mentioned. 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

Investing Articles

The BP share price could face a brutal reckoning in 2026

Harvey Jones is worried about the outlook for the BP share price, as the global economy struggles and experts warn…

Read more »

Midnight is celebrated along the River Thames in London with a spectacular and colourful firework display.
Investing Articles

How on earth did Lloyds shares explode 75% in 2025?

Harvey Jones has been pleasantly surprised by the blistering performance of Lloyds shares over the last year or two. Will…

Read more »

Group of four young adults toasting with Flying Horse cans in Brazil
Investing Articles

Down 56% with a 4.8% yield and P/E of 13 – are Diageo shares a generational bargain?

When Harvey Jones bought Diageo shares he never dreamed they'd perform this badly. Now he's wondering if they're just too…

Read more »

Number three written on white chat bubble on blue background
Investing Articles

Could these 3 holdings in my Stocks and Shares ISA really increase in value by 25% in 2026?

James Beard’s been looking at the 12-month share price forecasts for some of the positions in his Stocks and Shares…

Read more »

National Grid engineers at a substation
Investing Articles

2 reasons I‘m not touching National Grid shares with a bargepole!

Many private investors like the passive income prospects they see in National Grid shares. So why does our writer not…

Read more »

Number 5 foil balloon and gold confetti on black.
Investing Articles

£10,000 invested in Greggs shares 5 years ago would have generated this much in dividends…

Those who invested in Greggs shares five years ago have seen little share price growth. However, the dividends have been…

Read more »

Rolls-Royce Hydrogen Test Rig at Loughborough University
Growth Shares

Here is the Rolls-Royce share price performance for 2023, 2024, and 2025

Where will the Rolls-Royce share price be at the end of 2026? Looking at previous years might help us find…

Read more »

Investing Articles

This FTSE 250 stock could rocket 49%, say brokers

Ben McPoland takes a closer look at a market-leading FTSE 250 company that generates plenty of cash and has begun…

Read more »