If you depend on a secret for your security, what do you do when the secret is discovered? If it is easy to change, like a cryptographic key, you do so. If it's hard to change, like a cryptographic system or an operating system, you're stuck. You will be vulnerable until you invest the time and money to design another system.

As in most subjects relating to money management, there's a wide diversity of opinion on portfolio concentration versus diversification.

I'd say the general outline of a sound investment approach is, first of all, you have to decide are you going to try to be an investor yourself? The answer for most people is probably they shouldn't try. You should put your money in index funds and not try to be a stock picker.

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