At what stage of a painting do the shapes take on meaning? It helps to think about this if you'd like to take advantage of opportunities to let the paint display its watery qualities. The photo below, for example, is all about hazy light. If you set out to duplicate it right from the start, chances are it would take on a stiffness that would change the feeling significantly. Some features of the image are essential, but not everything needs to be "correct". Taking some time to consider where you need to be careful and where you can be carefree opens your brushwork, allowing the paint to flow. It is just as common for a painting to be ruined by too much control as too little.
Near the center along the bottom of the picture there's a brightly lit bush. Would the scene still work if you moved that bush to the left or the right? What if you stood it on end? In fact, the precise location on the page is not what is important about that shape. I actually think it would be better composed if the bush and the patch of sunlit ground directly below it were offset a little. What really is essential? Color? Value? Edge quality? Experiment a bit to see.
As an alternative to striving for accuracy, it is very useful to devise a few rough guidelines for handling the stages of a painting. Try filling in the blanks in the following sentence: "As long as the shapes on the ground are _____, _____, and ____, they will work just fine. There are an infinite number of perfect solutions to every watercolor situation, not only the one in the picture.
It may seem easier to just do what "reality" dictates and not have to figure anything out. After all, if it looks good like that, why change it? Because nothing is more important than the paint! The more you control the movement of the paint, the less it looks like watercolor.
The shadow pattern on the ground is definitely an essential part of this scene, above, but the exact distribution of marks is open to interpretation. Whatever you do will work as long as it is ____, ____, and ____. Diagonal? Soft-edged? Blue-grey? As dark as the green foliage? What do you think? A quick study can be designed to answer any lingering questions. I'm wondering, for example, if hard edges would be ok for those shadows. I wouldn't need to paint the whole picture to find out. Just a little comparison of the possibilities, out of context should reveal what I want to know.
When in the sequence of layers do the shapes take on meaning? Ask yourself "What would this scene look like with only the darkest darks?" Would the content still be evident? If so, you can be sure that the lights and the middle values can be treated very casually.
For homework, have a go at one of these, or find an image on your own. Narrow down the list of places where you need to be accurate. Widen the range of what is acceptable.
The less you correct, the fresher the paint will be.