[jellybean]

I, too, think that you want to go back, although you are not yet well enough to do so. If I were you, I would have a call with your principal, explain the situation, indicate that you very much would like to come back, but that it is possible/likely that you will not be able to return by February 1. I bet he (she?) will offer to work something out so you can take more time to recover. He needs you, and knows that he will be better off having you as an assistant starting in March than with a permanent replacement starting February 1. I think giving yourself more time to get better will make this an easier decision. If you quit now, when you feel better in a month or two you will be kicking yourself.