When studying art, even a short course, you will most likely have to go through repetitive rounds of practising values. I remember at my art school, we would spend months just painting and drawing what we at the time thought was boring still-life setups with white boxes, spheres, cones and drapes, placed in front of a white background and lit with a desk lamp. By doing this so extensively, my teacher ensured I understood the importance of values. In retrospect I know I learned a lot from these sessions.
Values are what create depth and focal points in a piece. No matter how much intricate and beautiful detail you’ve spent days or weeks painting, your piece will still look flat or confusing if your values are off. You should either start off in greyscale to establish a solid base with your values, or check them in greyscale throughout your entire creation process.