Art is making something out of nothing and selling it.
As a service provider you may not want to think of yourself as a salesperson. You're in the business of helping others, and the sales process may feel contradictory to your core purpose. If you're uncomfortable with the sales process, it's likely that you view it as unethical, manipulative, and dishonest. Looking at it that way, who wouldn't be uncomfortable?
Many service professionals also feel uncomfortable charging for services that either come easily to them or that they love doing. There is often a sense that if it comes easily and is enjoyable, there's something wrong with charging others for doing it.
Add the fact that service professionals sell themselves as much as they sell a product, and the whole idea becomes even more uncomfortable. It may feel like you're bragging and being shamelessly immodest.
Becoming comfortable with the sales process requires that you let go of any limiting beliefs you may have about being worthy of the money you're earning. In fact, developing the right comfort level also requires a shift in your perspective of the sales process itself.
Most people who are successful get paid to do what they do well. You don't usually become successful doing something that you find difficult. You become successful when you exploit your natural talents. Imagine Tom Hanks saying he shouldn't get paid to do movies because he's really good at ...