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Matthew Brown is head of advice development at Colonial First State in Australia. This article has been modified for New Zealand readers.

It takes a crisis like the global financial crisis to really see how emotion can rule over logic when it comes to our investment decisions.

Constant media coverage about falling share prices and declining fund performance helped to create enough panic among investors to cause them to sell up and invest in cash. The move may come at a cost in the longer term.

The problem is that while cash doesn't suffer from the same ups and downs as shares and other investments, there's a price for that peace of mind.

You lose the advantage of already being in the market when confidence and prices recover. It means that you may have sold when prices were low and, to get back into the market, you may be buying at levels higher than you'd like - far removed from the adage "buy low, sell high".

Hot potato

Investors flee the markets in droves when prices are at their lowest. It's partly fear, as they watch the value of their portfolios drop, and partly the strong desire to follow the crowd, a sort of "reverse gold fever".

Fear of missing the boat

And when markets trend higher, more investors than ever are attracted to the activity. This is fed by the views of friends and family as they share their views about buying and selling at that particular time and by increasing media and internet coverage.

When markets are rising the term "irrational exuberance" is often applied to the frenzy of buying, after the former US Federal Reserve chairman Alan Greenspan used it in a speech in 1996, causing a strong reaction in global sharemarkets. Of course there is also "irrational pessimism".

Cut my losses?

But history shows that those who are able to withstand short-term fluctuations in their portfolios can look forward to improved growth over the long term.

We are our own worst enemy, writes finance guru and economist James Montier in his book The Little Book of Behavioural Investing. We are all prone to stumble into "mental pitfalls", according to Montier. "This is true in investing as it is in every other walk of life."