exercise is great BUT if you are too exhausted,
this might help, find a comfortable position, lying down or sitting,close your eyes and imagine doing your favourite exercise, whatever it is,like imagine yourself walking through a beautiful forest in the springtime.But really feel each step you take,as if you are actually doing it.
This kind of 'exercise'has been helping me alot lately,because I have been housebound for weeks.
It can really lift your spirits.