It's all about self-control and money management IMO, and with that, you can be safe from doing other "stupid" things as well. Even with trading or investing, these two things are still crucial.
Anyway, I learned it from my uncle. He should've been one of the richest guys in the town, but his gambling problem turned him into just an average guy. Imagine what will happen to average Joes? Yep, debt and forever poor.