Painting is capable of making me feel like my cortisol levels are dropping while I work (good days). It may also feel as if idea bones are being extracted through the pores in my head with tiny pliers (bad days). In either case, there is always a moment during the process--and this has happened with every piece I have ever made--where I hate what I've done: I'm sure that it's terrible and I'm terrible and everything's terrible.
The other extreme is the purest joy. Whether it's from articulating an idea as closely as possible to its conception, or finding the power in an abstraction, making a successful piece is a singular feeling. I find peace knowing that while it may be improved upon, it was indicative of my best work at the time.
The tendency to work in series probably stems from my love of sequential and thematic art, and my vague need for order and discipline. I have many more series planned, but it may take a few more lifetimes to execute them all.