Passion is definitely not an illness nor is it fixation to exclude all others. Glad well talks about the 10000 hour rule, that it takes 10000 hours of study/work/attention/passion, to be an expert. The beatles spent that playing three shifts a day and several on the weekend in hamburg, working on knowing as much as they could and working and experimenting hard. They still had time to do other things, but their passion kept them keen and excited about their art.