From underestimating the chances of stock market crashes to the wrong asset classes, just because an investor is experienced doesn't mean they can avoid all the pitfalls.
Many investors make the fundamental mistake of being invested in the wrong asset class at the wrong time, according to Murray Smith of pension and wealth management firm Mattioli Woods.
He said that knowing the technicalities of investing such as Sharpe ratios and standard deviation won't help if an investor is in the wrong asset class in the first place.
"The biggest mistake is being in the wrong asset class...you can invest in the best funds but if you are in the wrong asset class it is no good," he said. "We would rather take a view [that an asset class isn't the right one] and come out of that asset class and lose a bit than stay in and lose a lot of capital."
Smith said that it was harder for investors these days to work out where they should be invested, even if they are old hands, and investors should be aware of just how quickly markets move.
"The markets move so much quicker nowadays and you need to be aggressive about your decision market. Trading around the edges of the portfolio is not going to drive performance," he said.
When markets get volatile, or worse, there is a financial crash that is the time even experienced investors are most likely to make a mistake.
Scott Gallacher, chartered financial planner at advice firm Rowley Turton, said the first mistake that is made by sophisticated and experienced investors is that they underestimate the number of stock market crashes that actually happen.
"Even the professional underestimate the number of crashes we have," he said. "They come about every five years without a warning but the thing is, if everyone predicts a crash all the time they will be right at some time but no one can predict a crash at the right time."
After a crash, investors continue to make mistakes, with Gallacher pointing out that many believe they have the risk tolerance to buy back into the market when prices are low but few actually do, and more are likely to commit the investor sin of selling at the bottom.
"A lot of people will sell out but it takes a lot of gut to buy back in,' he said. 'People underestimate the impact of the crash and in time people think they are more risk tolerant than they are, but in fact most don't want to be in equities at the bottom of the market."
Smith agreed that investors who have been investing money for a long time can still get carried away by a good stock market run.
"When things are going well there is still the belief that it will carry on," he said.
He said that stock market falls paralyse other investors so they are unable to make a decision about what to do.
"After [the last crash] you had years where clients were unable to make a decision. That is starting to change now and people want to invest but people have to make a lot of decisions when investing money and for many that is very difficult."
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