Sue, you actually make a good point. I think it is important to visualize your final painting (with or without sketches, though beginners should sketch). However, it is equally important to see what your painting is telling you and go with the flow. Especially in watercolor because it really can have a mind of its own and fighting it is not always best. There has to be a balance. Again, something that is hard to teach and really can only be taught by practice.