Some things don't last forever, but some things do. Like a good song, or a good book, or a good memory you can take out and unfold in your darkest times, pressing down on the corners and peering in close, hoping you still recognize the person you see there.

This quote is saying that some things in life do not last forever, but there are some things that will never go away such as good songs, books or memories. Even when we are feeling low and unhappy, we can take out our memories and login to them like we would a book. When we look at our memories we will recognize who we have become and know that even though times may be difficult, we still have those memories to look back on.