What illuminates our hearts

If it is the light that illuminates our surroundings, what illuminates our hearts? Why do we need to see someone whose voice we are happy to hear? Friendships, friendships that warm our hearts, why have they retreated to their caves in this century? These are really hard to understand. Best not to think at all. If he is going to think, let the person think about the beautiful, if he is going to talk, let the beautiful person speak or be silent.