I agree with justdust, plus I found that what helps me a lot is riding on the roughs, i.e. off the groomed slopes. I made a point of always hitting the sides of the runs this year, and the payoff has been a huge improvement in my stability and my ability to recover my balance when things start to go south.
When you're going faster, bumps and jogs on the slope hit you harder and faster and more often. At some point you start to feel like it's coming faster than you can react to, and that's when you shut it down. But practicing things that improve your reactions will improve the speed that you can handle.