Survey reveals top millionaire mistakes with investing

A new survey of over 230 global high-net-worth (HNW) investors worth over $1.5 million has found there are several lessons yet to be learned by the world’s wealthiest individuals when it comes to their investment decisions.

The research, conducted by global financial advisory deVere Group, was designed to offer guidance on how HNW and other retail investors could “optimise” their investment strategies to achieve their financial goals amid ongoing market and environment changes.

The top three ‘mistakes’ determined by the survey included an overreliance on cash, allowing emotions to drive financial decisions and an overreliance on historical performance as an indicator of present or future potential.

“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findings are a powerful reminder that even those with significant wealth can fall victim to behavioural patterns and outdated ideas that undermine their financial goals,” deVere Group chief executive, Nigel Green, said.

“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.

“Importantly, these lessons are just as critical for everyday investors as they are for high-net-worth individuals.”

Just under half of survey respondents (44 per cent) said they believed holding cash investments for long periods of time would provide some security for their portfolios, especially during market volatility.

“While cash has its place in a balanced portfolio, leaning on it for too long can be a major setback,” Green said.

“Excessive cash holdings often erode real value over time due to inflation. In addition, cash doesn’t generate returns or allow investors to take advantage of opportunities in equities, real estate, or other growth sectors.

“Instead of sticking with a ‘cash is king’ mindset, investors should recognise that true wealth growth comes from deploying cash wisely across diverse, income-producing assets.

Around 31 per cent of survey respondents also said they let their emotions guide their financial decisions, as Green suggests fear and greed would lead to more “impulsive” choices.

“The market rewards those who remain objective and disciplined. Emotional investing rarely leads to sustainable returns,” he said.

“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.”

Lastly, 21 per cent of the HNW individuals surveyed said they equated past performance with future opportunities.

“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,” Green said.

“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.

“These common mistakes are not unique to the wealthy—they are universal. Whether you’re a millionaire or just starting out on your investment journey, 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.”