I found - over a long period of time - that if I could identify what triggered them, I could try to avoid those situations. Some of it is a matter of confidence - I don't want to tempt providence by saying it doesn't often happen to me now, but I have learned to live my life to accommodate those situations, not to let the fear of them rule my life.
It's a very difficult thing to describe to people who have never had one - I froze solid in the middle of the icy road last weekend, terrified that I was going to fall over (but I wasn't) - never mind that I was in more danger of being RUN over!