You can argue that not every stock goes up long term, in which case, you’d be right. There are plenty that stagnate, while others fall apart completely.
And how can you tell which is which, especially given the second quote: “No rule always works, the environment isn’t controllable, and circumstances rarely repeat exactly?”
To that very good question, I would make three recommendations:
Know your pain vs. pleasure tolerances.
Allocate your portfolio appropriately.
Know each company’s actual value before you buy into it.
As Marks says, “Investing requires just one thing: dealing with the future.” And the future is undoubtedly going to be filled with emotions, failures, and corrections.