"I often hear people say what you said, "...until it does not work anymore". If it stopped working it could not have been based on the basics of price movement, could it?"
I think this is completely wrong, and to be honest it's going to interfere with your ability to adapt to markets and make money in any environment. Of course things go through periods where they work exceptionally well, and then sometimes stop working, that's trading.
It doesn't have to bankrupt you before you realize it's not working anymore. If you understand what's going on, you should be able to realize it's diminishing effectiveness well before you start losing money at it.
I've cycled through many trading systems over the years, yet not a single one of the "retired" strategies ever had less than 7% annualized returns, and never had a losing year. There doesn't have to be money lost in order to abandon a strategy. But they become retired when they no longer work to the efficiency levels I'm targeting.
At that point you move to something else that has a higher probability of working, rinse repeat...