What is flux? 60 days out

After more than 60 days from chemo, I am still having problems with my hands and feet although not as severe as a few weeks ago. Definitely have more mental clarity, but still fatigue and not sleeping well all at the same time. If I exert myself one day, I may pay for it the next two days with fatigue. Keep moving a few things off my to-do list here and there, and hair is returning, eyebrows, eyelashes etc. But D. and I were discussing the fatigue this morning and he told me it as just because I am in flux - but what is flux? Is it positive or negative? We all hear that phrase but what does it really mean? It isn't flex, like flexible, flex-time. It isn't flax as in the material or linen. But what is flux exactly so I can know when I'm in it or not? Apparently flux is a flow like the flowing of the tides, but it can also be a rate of flow in laws of physics. A little too scientific for me. Tidal flow sounds better and is more me right now, some days I have energy and can focus, not how it used to be but better than it has been. Still not high tide, and not low tide either. So, being in flux is not a terrible thing and at least now I know what it is.