[He's spent weeks being weak and sleep-deprived and injured and human, and you'd deny him a little happiness after all that? ): ...Nevermind that he's also a little happy that his master is sick and weak. It's as close to wholesome happiness as Sebastian gets.]
It is much to take in, I understand. Of course I understand if you would rather not accept food under these circumstances, and it is a poor substitute for a proper explanation, but would you care for some hot chocolate? It is free.