Jesus' preachment of love of one's neighbour as oneself is impossible to follow in all fullness until one has attained the height whereon his own true self dwells. Obedience to it would mean identifying oneself with the neighbour's physical pain and emotional suffering so that they were felt not less keenly than one's own. One could not bear that when brought into contact with all kinds of human sorrow that shadow life. It could be borne only when one had crushed its power to affect one's own feelings and disturb one's own equilibrium. Therefore, such love would bring unbearable suffering. By actively identifying oneself with those who are sorrowing, by pushing one's sympathy with them to its extreme point, one gets disturbed and weakened. This does not improve one's capacity to help the sufferer, but only lessens it. To love others is praiseworthy, but it must be coupled with balance and with reason or it will lose itself ineffectually in the air. Not to let his interest in other matters or his sympathy with other persons carry him away from his equilibrium, his inner peace, but to stop either when it threatens to agitate his mind or disturb his feelings, is wisdom.
-- Notebooks Category 6: Emotions and Ethics > Chapter 2: Re-Educate Feelings > # 129