All your senses get dulled. At my worst, I literally did not see/notice any of the dust and dirt that these days has me vacuuming when a fraction of it is present. I didn't notice how crappy I was dressing or how crappy I looked (pale, dark circles, thousand yard state) or how crappy I probably smelled. I never got complaints but these days I'm far more sensitive to personal cleanliness and taking out the kitchen garbage religiously. And it was not primarily apathy - these things I literally did/could not detect. I was basically wandering around life in a haze - a haze which again, I didn't realize was present. On some intellectual level I recognized I "should" care about these things but was too exhausted to ever get past merely existing.