Here’s my two pence worth, I’ve been snowboarding for 25 years and been on lots of different courses/lessons etc. I’m away on a 2 week riding/instructor course end of the month.
Flat light, slow down and look for shadows on the ground that you can use to turn on. Your not going to be carving, skidded turns will keep your speed down and let’s you “feel” what the conditions are. Try to stay in an area you know, it helps when you know what’s ahead.
I’ve had the weird “don’t know if your moving” scenario, pretty freaky when you think your still and a piste pole hits you at 20mph!
Ice, proper ice is blue and your not going to be turning on it. Go straight and slow/turn on something soft.
Hard pack, compacted snow, again slow down, if your struggling, your riding beyond your ability. There’s little grip available so you need to take it easy with your edges, big turns using as much of the piste as possible, if there’s snow at the piste edges, use that to turn on.
With out sounding patronising, have you had any lessons? I see so many good riders fall apart when the terrain get steeper or conditions aren’t too good. A good solid technique will get you down (in style) any slope.
Just an exercise to try, on a good day, put your hands behind your back, or on your bum and see how long you can keep them there whilst riding. If you can’t, lessons will help.