Answer:

Body parts don't literally have individual emotional experiences. And, as Paul suggests in this verse, it's not entirely possible for one body part to be "happy" when some other part is deeply suffering. People don't really notice their hands are feeling fine when their feet are in agony. Bodies are single organisms. If one part of the body suffers, the rest of the body suffers along with it. The hand will do whatever it can to relieve the pain in the foot and vice versa.