I'm not sure how common this is, but it was the problem with me and a few others I know. What I started drifting I often used the throttle too much, I tried to use the throttle to control how far the back of the car came out, this isn't the best technique I found. It is better to treat the throttle as a tool to keep the rear end slippery, only use enough throttle as you need to keep broken traction in the rear. Use your steering wheel to control the slide, this is a much better way to learn and will set you up well for later on when you start doing 120km/h+ corners in the dry. Much better to control the slide.
Also, a good seat makes a huge difference, same with steering wheel.