I never want to stop learning. I always have a curiosity about how things work. The least favorite part I think is having to constantly lobby for money for research and the resources to do things in the space program. I think it's essential that we have a space program. Technologies that spin off are going to help us in the long run.
Moneys are tight and space research is expensive, but it's a unique tool.
So you spend a lot of time trying to convince the government to spend money on these various areas. In part it's good because it allows you to think about why are you doing what your doing, but after a while, if you have to keep explaining it too often, you spend too much time doing that and not enough time working on the actual project and thinking about the science and what your trying to study. So that becomes frustrating. There's just too much to do. The basic goal with the space program is understanding muscle biology so that humans can be in space and not have any kind of permanent muscle defect, that affects their performance or health.