Drawing accurately is a difficult task. Artists talk about the excellent draughtmanship of certain artists with reverence. Pierre Prud'homme is in this top position for excellence. His drawings are not only accurate, but beautiful. DaVinci and Thomas Eakins also reign at the top. One might think all master artists draw with superb accuracy, but they don't. Their work might be beautiful, but not perfectly "accurate". It doesn't mean that those works are somehow "less than". Their skills are indeed excellent, but as in all things, there are those who just rise above the rest.
So how does one become a good draughtsman, let alone excellent? My son had a violin teacher who used to say, on a very regular basis, "... to go fast, you need to go slow...'' It seems so paradoxical. How can slowing down actually speed things up???? Going slow means taking the time to truly measure. Like the other adage, "measure twice, cut once", the same is true for drawing. Only instead of measuring twice, one may need to measure 3, 4, 10 times, or what ever it takes to get it right. It means taking the time to relate how one part of the drawing fits with other parts of the drawing. It also means don't get wedded to your work. You have to learn to separate yourself from the work itself. You have to be willing to change, erase, re-do. But there is more. It means taking as much time as it takes to get it right, and remembering that it isn't a race. Because once the drawing is accurate, everything else goes so much faster and easier.
And isn't this true for most things in life? To go fast, go slow. It will not only save time, but you might also learn and see something new along the way.