I have challenges in ensuring each light values are consistent. Sometimes it's getting lighter when my pencil starts to get dull, but after I re-sharpen it, it became too dark again

Was tougher than I expected, and I might have gone overboard with details but the exercise did help me clarify the surface forms. My 8B graphite pencil isn't as dark as I had hoped, so the value difference between light and shadow isn't as large as I wanted...maybe it's time to learn to use charcoal haha