Yes, so the exact definition of "have-to" and "want-to" already present some difficulties in pinpointing what exact the theory says.

In my personal experience, it's not so much "fear" than fatigue and frustration. I also don't feel that my desire to read reduces; it stays intense, but my brain just can't keep absorbing information, and I find myself keep rereading the same passages because I can't wrap my head around them.