Whether it is chasing returns and buying at the top of the market, or avoiding out-of-favour areas even though fundamentals suggest they are a screaming buy, the past 20 years have presented investors with a number of potential investment banana skins.
And many have slipped over on more than one occasion.
Here, a selection of very honest industry experts highlight some of the investment decisions they wish they had never made.
Even more importantly, they highlight the lessons they learned from the experience.
Chris Spear
Chris Spear (pictured), managing director at Spear Financial, says he was slightly hot-headed in his youth and chased returns from the then booming Japanese smaller companies sector.
"Timing, timing, timing – that has always been the biggest for me," he said.
"I am obviously a lot more experienced than I used to be, but judging market timing is still one of the most difficult things for investors to get right."
"I have got to go back to the mid-1990s when I made my biggest mistake. There was a fund that I absolutely loved, which was the Invesco Perpetual Japanese Smaller Companies fund."
"It couldn’t do anything wrong in my eyes as it had returned something like 200 per cent the year before."
"I do think it could perform well again, but because of what happened to me I wouldn’t put clients into it."
"I got it totally and utterly wrong in a big way. Ultimately, Japan fell off the cliff and the Invesco fund was one of the worst hit."
"I think fundamentally, everyone loved tech at the time and saw Japan as the leading innovators of technology."
"The amount of money going in just wasn’t sustainable, as investors were expecting completely unrealistic levels of returns."
"It is something that I have learnt from and it is something I actively tell investors, because of that experience I would say I am more low-risk and cautious these days," he added.
Our data shows that Invesco Perpetual Japanese Smaller Companies has returned 70.8 per cent since January 1995.
Performance of fund vs sector since Jan 1995
Source: FE Analytics
However, as the graph shows, market timing has been hugely important. The fund lost more than 50 per cent in the late 1990s, and more than 75 per cent in the aftermath of the dotcom crash.
Andrew Merricks
Andrew Merricks (pictured), head of investments at Skerritt Consultants, says he made the mistake of being overly exposed to tech stocks during the IT boom.
"We’ve all made mistakes," he joked.
"One of mine was during the tech boom. It was a case where I thought I was investing in different funds and was diversified, but actually I was holding the same stocks, just in different portfolios."
"I’ve seen it with other people as well; for instance one of them held both Invesco Perpetual Income and Invesco Perpetual High Income. It’s the same with holding a number of emerging market funds – the stocks are very similar."
"I held the Framlington NetNet fund, Aberdeen Technology and Gartmore Techtornado. The Gartmore fund folded and the Framlington fund quickly became 'not not' – not 'NetNet!'"
"I have obviously learnt my lesson from that experience, but the other thing I have learnt is that just because you hold something that is out of favour, it doesn’t mean it is going to bounce back."
"Take an investor who has £10,000 and that falls to £8,000. For some reason the logic can be to wait until you get back up to £10,000 and then sell. That is ridiculous. You are far better off selling then and trying to find new opportunities elsewhere."
"Bill Mott made a very good point about buying out-of-favour stocks. His example was that you might as well bet on West Ham to win the league and for Manchester United to get relegated if you use that logic."
Gavin Haynes
Gavin Haynes (pictured), managing director at Whitechurch, says that one of the biggest mistakes he has made was to ever believe the hype around investment fads – such as the tech bubble.
"The advent of the internet undoubtedly changed the economic backdrop in many areas and provided some exciting opportunities for investors," he said."However, it also resulted in investors forgetting the basic principles of investing. Whilst painful at the time, the lessons learnt have stood me in good stead over the past decade."
"These included following [Warren] Buffett’s mantra of being fearful when others are greedy and vice-versa."
"Also, if someone talks about a 'new paradigm' or that it is 'different this time', then be very careful, as it rarely is."
"Focus on traditional valuation measures and be wary if someone comes up with a newfangled way to value a company."
"I remember something called 'eye-balls per screen' being used to talk up the merit of non-profit making internet start-ups."
"If you cannot understand how to value an investment, then it is best not to get involved, irrespective of the growth prospects."
"Needless to say, when Facebook was floated I was not in the queue to buy shares," he added.
