By far the greatest lesson I learned was by reading about the lives of artists. So often you discover that many great artists ended up deeply unsatisfied with their careers and work through difficult relationships with studios and publishers. It is so tempting to sell your creativity to the highest bidder, but the cost is often one of diminishing returns in terms of personal artistic expression. Staying true to the reason you started drawing in the first place is every artist's greatest challenge, but if you're not going to fight for that, then what else is there?