[randlet]

"In poker, you can play perfectly and still lose."

Only true over the short term: all you have to do is play GTO poker over an infinite number of hands in a rake free game and you should at least break even I think!

That said, this fact is the main reason that the game of poker really "works". If playing perfectly (or at least at a much higher level than your opponents) allowed you to always best your opponents, then you'd quickly find yourself out of opponents. There needs to be enough luck involved to keep losing players coming back to the table (the same reason most casino games have a thin house edge).

Poker can be an absolutely soul crushing game to play professionally. "Running bad" where you lose money over 10's or 100's of thousands of hands even while playing well can make you seriously question your sanity. It can also cause you to add subtle (or not so subtle) errors into your game (e.g. playing too cautiously or aggressively) which can turn your once winning game into a losing game, making it tough to decide whether you are currently a winning player running bad, or actually a losing player.