@robbery I have had similar problems but started taking more commissions because I want to earn money and develop more professional habits.
Something that is helping me make the transition from only doing personal work to doing commissions is giving friends/family a discount if I have complete creative liberty over the subject so I can focus on making a good piece without worrying. This works well for people who are close to me. I also started a Threadless shop that sells my art on prints and shirts and I found that helped a lot -- most friends/family are honestly just hiring me to be friendly and show support! They would rather pay a smaller price for a cute item than go through the process of a full commission.
If they want something more specific, then it has helped to check in with them throughout the process to get feedback and make sure I'm not wasting time making something they don't like. Before starting the drawing I make sure I know which of my art pieces they like the most and I brainstorm a little with them. And then I trust that they hired me because they like my style and judgment, so I try not to listen to the self doubt. I focus on making a piece that makes me happy while matching their criteria.
Even though it's not efficient, I try not to give people work that I don't feel a "spark" with. It feels bad, and then it can end up being a worse and worse problem if other people see that piece and want something similar, because I will be trapped in making things that I don't like. On bad weeks I end up spending twice as long or three times as long as I am being paid, but I am thinking of it as training and having the mindset of always wanting to work faster and communicate better to get ready for higher stakes. I would rather make something good and then learn how to do it faster than make something disappointing because I want to be speedy.
I am still learning so I will look forward to reading everyone's posts on this topic!