I've only been investing for a few years now, but I think it's important to tell newcomers that we are currently in a bull market where pretty much anybody can see a 20-30% return fairly easily. It's common to become overconfident during a bull market and begin to invest more and more... nobody can predict when the market takes a negative hit with 100% accuracy, but history dictates that a massive blow to the market will occur at some point in the future. Only invest what you can afford to lose, and watch out for warning signs (war, disease, tariffs, disasters, etc.) of the market taking a hit due to external factors. Also don't forget to take your profits, after all you only actually make money when you pull out.