This whole passage in Being and Time is really interesting to me. Heidegger is talking about how we may have a way we take a stand on our being (live according to some ideal we have for ourselves) with or without knowing it. In another sense, the knowing of one’s Being is not necessarily the same as being familiar with it. We can be familiar without knowing something in an intellectual sense, as that is only one way in which to engage with our world. But being familiar is a more basic aspect that is always a part of us just living and being according to how we want to see ourselves in the world (taking a stand on our Being).
Bearer of Pity 