The attached note takes a look at the impact of investor psychology. The key points are as follows:
Investment markets are driven by more than just fundamentals. Investor psychology plays a huge role and helps explain why asset prices go through periodic booms and busts.
The key for investors is to be aware of the role of investor psychology and its influence on their own thinking. The best defence is to be aware of past market cycles (so nothing comes as a surprise) and to avoid being sucked into booms and spat out during busts. If an investor is looking to trade they should do so on a contrarian basis. This means accumulating when the crowd is panicking, lightening off when it is euphoric.