Any time you limit your palette, strokes or time, you begin to understand the value of distillation, "the extraction of the essential meaning or most important aspects of something."
I don't think you'll hate the exercise as much as she says, but it will push you around and give you a new way of looking at effective strokes. Let me know how it works for you.
And definitely go look at Jo's YouTube page for more instruction in watercolor. Good basics here, simple, helpful and clearly presented. Enjoy!