The Top Investing Mistakes That Even Millionaires Make

A new survey by deVere Group, one of the world’s largest independent financial advisory firms, reveals the most common investing mistakes made by millionaires. These insights, while focused on high-net-worth individuals, are just as relevant for business owners and anyone looking to optimise their financial strategies in today’s rapidly changing economic landscape.

The survey, which polled over 230 individuals globally with investable assets exceeding $1.5 million, highlights key lessons that can help business owners avoid common financial missteps.

Nigel Green, CEO and founder of deVere Group, explains: “Our findings are a powerful reminder that even those with significant wealth can fall victim to behavioural patterns and outdated ideas that undermine their financial goals. These mistakes should serve as a cautionary tale—and an opportunity to refine approaches in a market where adaptability and informed decision-making are everything.”

Here are the top three mistakes identified in the survey and what business owners should take away from them:

1. Holding onto the ‘Cash is King’ Mentality for Too Long

The most common mistake, identified by 44% of respondents, was over-reliance on cash, with many believing it offers security, especially during volatile periods.

Nigel Green explains: “While cash has its place in a balanced portfolio, leaning on it for too long can be a major setback. Excessive cash holdings often erode real value over time due to inflation. Cash doesn’t generate returns or allow businesses to capitalise on opportunities in equities, real estate, or other growth sectors. Instead of sticking with a ‘cash is king’ mindset, business owners should recognise that true wealth growth comes from deploying cash wisely across diverse, income-producing assets.”

2. Making Emotional Decisions

The second most common mistake, identified by 31% of respondents, was allowing emotions to drive investment decisions. Emotional reactions like fear and greed can lead to impulsive choices, such as panic selling during downturns or chasing market trends at their peak.

Nigel Green notes: “The market rewards those who remain objective and disciplined. Emotional investing rarely leads to sustainable returns. A solid financial strategy, guided by expert advice and based on long-term objectives, mitigates emotional pitfalls and ensures investors avoid the classic ‘buy high, sell low’ trap. This is precisely why professional advice is so invaluable—it provides a critical layer of objectivity and helps keep emotions in check.”

3. Focusing Excessively on Historical Returns

Twenty-one percent of respondents relied too heavily on past performance when making decisions, equating historical success with future potential. This can prevent business owners from identifying emerging opportunities.

Nigel Green adds: “The classic financial disclaimer says it all: ‘Past performance is not an indicator of future results.’ Markets evolve rapidly, and strategies that worked a decade ago—or even last year—may no longer deliver the same outcomes. The most successful investors are those who evaluate the current landscape and anticipate what’s coming next. At deVere, we help clients focus on forward-thinking strategies to stay ahead of the curve, particularly as megatrends like AI, clean energy, and digital assets reshape the global economy.”

Lessons for Business Owners

While the survey focused on millionaires, the mistakes identified are universal.

Nigel Green concludes: “Whether you’re a millionaire or a small business owner, the same principles apply: avoid sitting on too much cash for too long, keep emotions in check, and always look forward rather than backward when making decisions. These results underscore the importance of stepping back and reevaluating ingrained habits. Financial success is as much about avoiding mistakes as it is about making smart moves. Expert financial planning can make all the difference.”

By addressing these top three mistakes, business owners can position themselves to maximise returns, safeguard wealth, and capitalise on the opportunities of tomorrow.

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