Life has its ups and downs. Some days I have a lot of energy and everything feels sweet, I can handle any number of unforeseen circumstances and laugh at the future. And other days, well... it's just not that sweet.
If you've lived with chronic health problems for a while, chances are that your good days are few and far between, and there are many days with very little energy, where you hardly seem able to tackle even the everyday challenges of normal life.
I find that just knowing this, and accepting it, can be very liberating.
Sometimes I have a lot of energy, other times I don't. The trick is to not identify too much with your perceived problems when you are in a low, because they always seem bigger then, and lacking the energy to deal with them, you may think that you will never be able to cope. But you can. Just recognize that you are low, you need to rest and do things which build you up, and don't make any big decisions based on how you're feeling at that stage.
Then get ready to surf the next wave.