[I] took some comfort from the thought that at least I still had my wits
about me. Or at least I felt as if I did. Presumably, a confused person
would be too addled to recognize that he was confused. Ergo, if you know
that you are not confused then you are not confused. Unless, it suddenly
occurred to me — and here was an arresting notion — unless
persuading yourself that you are not confused is merely a cruel, early
symptom of confusion. Or even an advanced symptom. Who could tell? For
all I knew I could be stumbling into some kind of helpless
preconfusional state characterized by the fear on the part of the
sufferer that he may be stumbling into some kind of helpless
preconfusional state. That's the trouble with losing your mind; by the
time it's gone, it's too late to get it back.
-- Bill Bryson. A Walk in the Woods (1997).