Help me out of this confusion!
Memory is one of the greatest of our faculties. The ability to retain information and experience is of vital importance. But it is a more subtle art to be able to cast out of the mind --or at least from a commanding place in it--failures, events, unhappy things that should be forgotten. It is a great skill to be able to be selective and say: "I will hold this in cherished memory. The other I will cast from me." To be efficient, to be happy, to have full control of your powers, and to go ahead successfully, you must learn how to forget.
What are "it"s in there? Are they pronouns referring to "memory"? Or are they so-called "preparatory subjects" referring to the following infinitives (i.e, to be able to cast out of the mind/ to be able to be selective and say)?
To me, they are both pronouns referring to "memory" because I think the author is talking about another function of memory which enables us to delete something we want to forget from our mind. But my text (written by a Japanese) says they are both preparatory subjects (like "It's easy to read the book=To read the book is easy)...
I would like to have your comments, teachers.