Such a question is so context-dependent that it becomes fairly meaningless. For example, in some cases (such as imminent risk of drowning due to a being in a c

Such a question is so context-dependent that it becomes fairly meaningless. For example, in some cases (such as imminent risk of drowning due to a being in a capsized boat), your next breath of air will be the thing you care most about in life. If a person has a new baby, taking care of that baby tends to become the thing they care most about in life. And so on. It's the kind of question people are instructed to ask in a marketing/networking tutorial, i.e. 'when meeting the client, try to find out what makes the client tick, via asking big picture questions and engaging in active listening.'