Downhill sports such as skiing, snowboarding, and bobsledding might represent:
Making progress smoothly, quickly, or well, possibly due to your own abilities or gifts (represented by the accessories or vehicle)
Moving past or over obstacles easily
Skimming over the surface rather than delving into details
A situation requiring great skill and responsiveness
Sports or competition
Taking a risk (it's easy to fall or go off-course)
Also consider the context. A pleasant downhill experience could represent fun and relaxation. An out-of-control experience could represent an out-of-control situation in your life, or fear of losing control.