CHD affected me in much the same way. One day I would feel great and could run up the stairs, the next I would be bound to a chair feeling very sleepy and lethargic. I would sleep for many hours during the day and not be able to sleep at night, while sometimes I would only sleep at night. Nobody could explain all this to me. I found eating any sized meal also drained me of energy very quickly, forcing me to fall asleep for about 2 hours. I kept a log of my activities trying to establish if something I was doing made me have more energy on some days, but there seemed to be absolutely no relevance.
Interesting questions. Pericarditis has the same symptoms, a general feeling of weakness, fatigue, or lightheadedness. As well as shortness of breath, muscle aches, etc.
It is reasonable to expect feeling well one moment and not the next. There shouldn't be any difference of symtoms and signs distinquished by source.
To reverse days and nights doesn't seem to be pericarditis related.
Thanks for your questions.