Ali loves dinosaur books, and he has one from the library right now. He doesn't get the whole concept of borrowing books very well, though, and thinks of it as his. Leila was looking at this book, and he got very upset, because of this feeling of ownership. Later he had calmed down and we were looking at the book all together. Then he said "this is my book."
"Actually," I told him, "this is a library book. We have to take it back to the library." This elicited loud protests, so I explained that the fun thing was that we could borrow it whenever we wanted, and we could borrow other dinosaur books, too. Calm now, Ali looked at his book and leaned down to kiss it. Deciding just before contact to blow the kiss instead- "I'll miss you," he said.