In this picture, for example, I can foresee some trouble getting the mass of green that surrounds the sheep to be a smooth, clean wash. With all the care I might choose to take painting around the sheep I could end up with streaky, overlapping brushstrokes. This is the kind of problem I could easily overlook, though, since the grass is not the real subject of the scene. My attention goes right to the sheep, so I'd probably consider how to paint them first. If I feel confident about translating them into layers, I'd think, "OK, I'm ready to paint". Then, when I got to the grass, I'd discover too late that I was not as confident about that part.
Five minutes is plenty of time to devote to an honest assessment of what may be tricky for you, and to devise a study that will give you the answers and the practice that you need. If you are concerned about undoing your precious spontaneity, you needn't be. A little practice will not turn the process into a dry, cerebral activity. As soon as you make a stroke on a new sheet of paper the juices will start to flow. The only difference is that you'll be more confident, and won't have to shift gears for the tricky bit.
By the way, if you paint this picture, consider moving that fence post.
Here are a couple of images to think about. Write down what your unanswered question was, and how you chose to look for an answer.