Books, stationary, and desk supplies are justified purchases. If a notepad with your name and phone number personalized on it makes you feel like more of a professional writer, then go ahead and make the purchase. Don't feel as though you shouldn't spend some money on the things you need to be an efficient writer; reference books for your desk are certainly a justifiable purchase, as are the various desk supplies you will inevitably need. You start to cross the line if you decide that a personalized coffee mug or a top-of-the-line computer system is necessary in order to work your magic, especially if you aren't earning enough money to cover the cost of these types of purchases. There are some things writers need, some things that writers want, and there are some things that writers don't need but they yearn for despite the price tag. Try to reserve these types of purchases as rewards for earning a substantial check from a writing job. Being a professional writer is a highly coveted occupation, so sometimes people who start out writing and meet with success will still have a hard time convincing themselves that they are indeed professional writers. Try getting into the mindset that you are a writer and pretty soon you will work up the confidence you need to apply for high paying writing jobs.