In my teens, my father traded commodities. Hogs, corn, soy, all on the CME (for a brief period, he worked on the trading floor, but then I came along). During this time, I provided IT support (this was in the early 90's), aggregating historical market data (hello Knight Ridder!), plotting charts (Supercharts, when it was still software and not a SaaS platform, on Windows 3.1), and so forth.

I saw first hand what happens when you're sweating the market going against your trades. My father would smoke heavily and not sleep at night.

Now that I'm 31, we joke about those times. I still build algos with Quantopian for fun (and share them with my dad over a beer, throwing the backtest up on a 70" TV), and make a few bucks here and there, but you would be fucking insane to try to be a day trader now (competing against people with crazy financial and technological resources).