system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If the golden rule of the stock market is to buy when low, sell when high, who is doing it the other way around?
gpt
The golden rule of the stock market is basically akin to saying that the golden rule of roulette is to always pick the winning number.

True, but not very helpful in practice.

If you knew exactly what a given stock was going to do in the next 24 hours you could make a fortune on almost any stock. In many cases you could actually do it without any startup money since under the right circumstances you can sell before you have to pay.

That's why insider trading is illegal, because even a vague idea of what a stock will do is really powerful. To reuse our roulette example it's like knowing whether a particular roll will be red or black. Not as good as knowing the number, but a hell of a lot better than random.