There are some good threads on various forums about when to do qigong, forms, and so on. I noticed I tend to feel much better at night time, between 11 p.m. and midnight, somewhat consistent with one answer. I’ve also always been a night owl anyway, so I have always had more good energy at night without working on any kind of qigong. My guess is I should just go with this pattern and exploit it. However, eventually I’d like to be able to wake up earlier and feel and work the same sort of energy.