Investors are prone to behavioural biases. I am guilty of some, which have caused me to commit investing mistakes and miss out on some of the best deals in the market. Here are two biases that have cost me dearly. Avoiding mega-cap companies One investing fallacy is that mega-cap companies can’t grow much.  Today, Apple, Amazon and Microsoft are each worth more than US$1.5 trillion. For those counting, as of 17 July, each of the trio was worth more than the entire South Korean stock market, which had a market capitalisation of US$1.4 trillion. Can companies of that size realistically grow much more? I used to shy away from mega-cap companies simply because I believed in the law of big numbers. It is much harder to grow meaningfully when a company reaches a certain size. However, when I looked back at records, I realised that the biggest company 25...