Everything everybody else said, but remember...
On the road, you have bushes, trees, roadsigns and other traffic which give you a sense of how fast you're going. You know how fast 80 mph feels on a narrow road between high hedges right?
On the track, all of that disappears. You have a big wide open circuit, usually with big wide open run off areas and everything seems slower. So when you think you're going into a corner slowly, just be aware that you may be travelling faster than you think.