I've become more flexible about this too, and it is very freeing. In the past, if I didn't finish a book, I automatically put it in the category, "I must not have liked it so no use going back to it; it's just not for me."

I even remember the book that changed my perspective on all this a couple of years ago - Less by Andrew Sean Greer. I ended up loving it (and have now also read and loved the sequel, Less Is Lost), that I no longer put any limits on stopping and starting again.