Even with trading, you can't really know if the strategy that you have made which might work first time is because of luck (crystal ball) or analysis. You might believe its analysis because why not but repeating that strategy consistently over a long period of time is downright near impossible.

And then you realize that most of the traders lose money and there have been systematically proven to be basically very little alpha if any and you are better off just investing within the index funds and focusing much more on increasing the amount of money that you can save (increasing your salary, finding ways to save money etc.)

https://www.bogleheads.org/ for those of you interested.