Since 2002, I’ve worked as an FCA-regulated portfolio manager, reviewing two to three investment portfolios almost every day. Over more than two decades, that adds up to well over 10,000 portfolios—ranging from ISAs and pensions to general investment accounts. Much like a doctor who recognises symptoms instantly, I can usually spot the problems within minutes. Patterns appear quickly. Human behaviour is remarkably consistent. Investors—regardless of age, experience, or wealth—tend to repeat the same mistakes.

These errors aren’t hidden technical flaws; they’re behavioural traps. From over-diversifying in the name of “safety” to holding on to losing stocks out of emotion, I’ve seen it all. And while most of these issues could be corrected with sound advice, the challenge is that many investors resist it—even when they know it’s true. Why? Because while everyone wants results, very few of us enjoy being told we’re wrong.