Humans are social animals, so I tend to agree. My hunch is that feeling, on a visceral level, that you are necessary to the people around you in some fashion is

Humans are social animals, so I tend to agree. My hunch is that feeling, on a visceral level, that you are necessary to the people around you in some fashion is what will keep the will to live burning bright. It can be actual or merely delusional - the important aspect being the level of conviction in the belief.