When we first start skiing at the beginning of the season we concentrate on the fundamentals. Stack, body position and rhythm perhaps even free skiing and our skiing generally improves quickly as we refine these fundamentals.
As the season goes on we want to keep improving so we start working on smaller details like the turn, our reach and perhaps where we are looking etc. (forgetting or letting the fundamentals lapse)
Unfortunately our fundamentals of stance and body position start to drop off when we focus on smaller details, and hence we start going down hill.
Revert back to your earlier keys that you were working on at the beginning of the season which were of a higher importance and your skiing will start to improve again.
Sometimes working on the fundamentals all season and trying to fully master them is the key to continual improvement.
We often fall into the trap thinking we have these skills mastered but find we haven't done so.