MSB Trading - 2020, page-12910

The reason people say “only invest what you can afford to lose” is because we have seen people do really daft things.
This is a story that is not about investing but it’s the same principle.
When I worked in banking, we had a customer in his 40s who had power of attorney of his father’s money. This was in the 1980s. The son would come in every day and withdraw money, for months. Each time we saw him, he looked sicker and sicker until one day he didn’t come in. A week passed. Another week. Then his father came in to tell us that his son had had a heart attack and was in hospital...only to then discover that $60 000 had disappeared from his own account and there was nothing left. As it turned out, his son had been putting money into a poker machine at the club...having exhausted all his own money, he believed that the machine would eventually pay out, and so he then put his father’s money into that poker machine. More than $100 000 went into that one poker machine. With no money left and no win...heart attack. That was a lot of money in the 1980s, you could buy two houses with $100 000.
I could tell you another 20 stories of people doing things like this with other people’s money, or money that they could not afford to lose. Only invest (or gamble) money which will not impact your life if you lose it. If your investment goes belly up, then you don’t want to have to pay a loan (be in debt), or move house (give up your lifestyle) or lose a relationship (emotional turmoil), or anything like that. If an investment goes belly up, you should be able to carry on in your life as you did before. That is what people mean when they say “only invest what you can afford to lose”.