It's a tough choice for me between sleep problems and post-exertional sickness. I've been completely nocturnal and that is really inconvenient and unpleasant for many reasons but I'm having a hard choosing which is worse. I guess I think PES is still worse. I guess if I had my choice I'd rather be nocturnal if it meant I could have the ability to do things without becoming extremely sick for abnormally long periods. So for worst symptom, PES/PEM it is.