One of my favourite investing articles is an old piece, written in February 2008, by The Motley Fool’s co-founder, David Gardner. It had the provocative title, The Greatest Secret of All, and an equally provocative lede (emphasis is his): “Welcome to my article. I’m glad you found it, because it is your lucky day, dear Fool: The greatest secret to easy riches in the stock market is contained right here, below.” The article does contain the greatest secret in investing, and I implore all of you to read it. I’ll come back to his piece and provide a link to it later. For now, let’s turn to my girlfriend’s investment portfolio. The portfolio In early 2019, my girlfriend wanted to build a portfolio of stocks for herself. We started having long conversations about what she can do and how she should be building the portfolio. Eventually, she settled on a...