Stress
Yes, you find your biweekly pottery class relaxing. But that's now. Once it's your job—once you pile on business loans, the struggle to meet the demands of a nonstop schedule, and can no longer muster the energy to clean the house after scrubbing down your studio—then pottery will be less relaxing.
You'll be constantly selling, selling, selling. Just this week you're at three farmers markets and an evening craft fair, then next weekend you're taking a night bus across state lines to meet a gallery owner in person. After that you're coming back for a day to exhibit your work at a local shop, and then it's back on the road to another art festival. Yikes. Oh, and don't forget you have to fill twenty online orders by Friday.
Maybe you should pick up a therapeutic hobby to unwind. Painting, anyone?