I once pointed out, to a former grad school roommate, a big fat general relativity textbook sitting on my bookshelf. I said that even though I didn't use it any more and had forgotten its contents, it was hard for me to throw it out. "Of course not!" he replied, "It's the only proof you have that ever knew any of that stuff."
It's gone now. I've gotten rid of most of my textbooks, but I still retain a sampling for sentimental reasons.
It's gone now. I've gotten rid of most of my textbooks, but I still retain a sampling for sentimental reasons.