My apologies if this sort of question has been posted before, I did a quick search but couldn't really look indepth as I have an eye condition that limits my computer time

Anyway, I was listening to the audiobook of Scott Cunningham's 'Living Wicca' and he said that when sick you should not do magick except for self-healing as it will be dangerous and ineffective. I hadn't heard of this idea before (I am very new to Wicca) but I was wondering how does this apply to chronic sickness? I have several chronic illnesses so I am basically sick all the time... does this mean I cannot / should not practice magick? Or only magick of particular kinds?
Any advice appreciated,
Spring Moon <3