The right side of your brain is the creative side and will enable you to develop new ideas and powerful imaginative and inspiring results. Using the left hand actually activates the right side of the brain. As right handed people do not normally use the right side of the brain very much, believe me, it needs something to activate it!
However, if you are already left handed, then I suggest you try doing the exercises with your right hand. What this does is allow you to concentrate more on ‘looking/seeing’ what you are trying to draw and less on pulling a ‘template’ type image from your memory (brain). Also, you gradually stop worrying about how well you have drawn, as you know that you can’t draw properly with your opposite hand. When you stop worrying, you begin to concentrate on ‘looking’. Drawing is really the ability to see. Once you are truly observing what you are looking at, your drawing skills simply improve.