Jack Johnson Lullaby does a great job capturing the sentiments of a man who must leave home for his work but will be home soon. So he leaves a lullaby behind to comfort his spouse or partner and also to try to do something conciliatory about his leaving i.e. to make himself feel better about leaving home. He has to leave because that's what he does, but he doesn't want to leave the one he loves. The classic wishbone that so many of us have felt.