Learn from your mistakes. When you first begin to write professionally, you will inevitably make a few mistakes here and there. Whether it is being too informal in your query letters to potential employers or not looking for jobs in the right places, you will soon learn that sometimes your way of doing things is simply not working. Pay attention to what works and what doesn't, and vow to not repeat your mistakes. For example, if an editor criticizes you for using too much passive voice in your writing don't take offense to the criticism and pout about the editor's comments. Instead, research what passive voice actually is and then don't use it in your writing anymore. You need to remember that you are in a position to learn a great deal from other people, and if you don't accept criticism graciously then you will never learn. Nine times out of ten the editor or buyer will have valid complaints and are certainly not out to hurt your feelings or make you feel bad about your writing…they are just looking for better writing from you.