Mouths can tip off what a person is feeling. It changes with the expression of the face. The nose and mouth work together. The shading and highlights are consistent. Plus the concave and convex areas above the upper lip extend to the nose. Try sketching any subject. Your family, pedestrians, classmates, babies, adults, children. You will become more courageous and confident at drawing. Sketch fast, look at the subject more than your paper. Start off with basic shapes and guidelines and draw away!