Also distinction between learning (mostly) and production (mostly). In investing, business and no doubt poker there is nothing wrong with a period of losing money while learning. But you better be aware and be learning and you better not tolerate that period lasting indefinitely.

I hear this often about investing: people get started (losing money) with grossly insufficient education and they do learn for a few years, then give up, move on and blame it on "the professionals" or "science shows". When the fact is, if you start investing and learning at the same time, most likely you will underperform everyone else for a while. It's not because you were stupid; it's not because of "the professionals"; it's that you didn't know. It's an important distinction, and the equally losing opposite of "sunk costs".