In English, the verb be is surprisingly big and important for its size. It has a whole lot of forms and ways to contract. It essentially means to exist or can be the linguistic equivalent of an enormous equals sign.
Today, I just am. This is the last day when I can be like this. Tomorrow will be different as I am going to be preparing for a new class. Then on Wednesday, I shall be with the new group.
I was off for quite a long time. If I were on break longer, I would be okay with it. Yet, so far today, I've just been and I am happy with that.