Two habits have caused me misery over time...
One that I had years ago is a very common one - letting my hands drop back after the pole plant. This, of course, is a terrible thing to do and causes all kinds of problems with one's turn. To fight it, I consciously started making my pole plants below and in front of me. I became *obsessive* about getting and keeping my hands in front. That helped my skiing, natually, but also introduced other problems.
Before long, I developed the typical cross-over pole plant and *that* took years to correct. On the rare occasions that I get video taped, I'll notice that I still have a hint of that cross plant with my left hand. (But going forward is better than dropping back, I guess.)
The second habit is related to this whole "lifting" question. Most of my learning years involved skiing powder and crud. I pretty much developed an equal-weighting style of two-footed skiing. That worked fine, particularly on the old "straight" skis, until I got onto hard snow and wanted to carve a turn. Back then, the thinking was to get essentially all your weight onto the downhill ski, and that was very hard for me to do consistently.
An instructor suggested "lifting" the inside ski from the moment of edge engagement (of what would be the downhill ski) all the way through the turn. That tip seemed to click with me, and I started doing practically all my groomed-snow turns that way. I ended up developing a habit of making turns with the tip of my uphill ski just grazing the snow and the tail of that ski about 3 inches off the snow.
So, that worked pretty well, I was getting my weight onto the downhill ski, I was forward (it's hard to do that if your weight is back), and pretty pleased with the whole idea.
Then, along come the new skis and railroad track turns. All of a sudden, you instructors want me to move some of my weight back over to the *uphill* ski! So, of course, I'm still stuck in my laboriously-ingrained habit of weighting the downhill ski.
Maybe I should try to become an instructor just so I'd be aware of these technique developments earlier and not spend so much time and mental effort forming habits that I'll have to break a couple years later.
Always behind the curve.