The heart is not only a hollow muscle. Since very ancient times, the heart has been considered as the symbol of life, desire, and passion. True love and desire both require a great amount of psychic work in order to give up narcissism, and abandon both egocentricity and hold over the other. Under these conditions, and even more so when they are mutual, love and desire bring up a lot of happiness and jouissance. However, in the event of non-reciprocity, or breaking up of the relationship, they may entail serious physical and psychic decompensation (depression, sexual impotence, cardiomyopathy, etc.), and even death (suicide or murder).
Love, possessivity, break-up