You know what I did? Because I was becoming frustrated, instead of thinking about the theories on spotlight, shadows, etc., which I couldn’t imagine even if I try, I focused on the lines and copied exactly where the dark shades and light ones were. And no, I wasn’t thinking about apples when I was drawing that.
Perhaps this could work for you...or not?😅

It may not look exactly like our desired goal, but it brought me closer to it