The advice is: you need to know whether you are in a: good state, acceptable failure state, unacceptable failure state. The rule: never ever ever ever get into an unacceptable failure state. Moreover, define an unacceptable failure state as such.
In my case, an unacceptable failure state had anything to do with potential chances to get irreversible damage. I am athletic in a few ways (e.g. running) but skiing hits all my bad points (balance, flexibility and reaction time). Learning how to ski was quite hellish for me, but my GF pushed me and I basically had little choice. On the one hand I'm grateful, on the other hand I still remember the pain too well.
So, how to get in an acceptable failure state all the time? I realized I needed to learn how to fall. The irony was that my ski-instructor never told me this, he simply taught me some very basic skiing skills but that's it.
Once you learn how to fail, you can get into an acceptable failure state :) You'll be bruised, but it's better than skiing of a cliff. For a long while (2 years), falling was the only way reliable way for me to break. Yes I could do a snowplough but it simply slowed my acceleration in the beginning and later it slowed my speed up to a point. I had to learn the hockey stop in order to find another way to reliably break. Your mileage may vary though ;-)
Good state, acceptable failure state, unacceptable failure state. Combine that with some basic ski lessons and a helpful skiing partner and you'll learn how to ski. I started at 27 against my will and can ski okay-ish on a red piste a few years later.