Rav S.R. Hirsch(Vayikra 19:18): You shall love your fellow as yourself – This rule applies to all our social activities in knowledge, speech, and deeds. Ahava (love) is the most elevated of our emotions in relationship to G‑d and man. The word “ahava” is basically the word hav (give) with the addition of the letter aleph which attaches it to a particular. Thus the meaning of the word ahava (love) is to devote oneself to another and to bring the other to oneself (See also the comments to Bereishis 37:4). Two individuals who function as one is ahava (love) as opposed to hatred (See Vayikra 37:17). Note that the Torah doesn’t say “Love your fellow” which is the normal way of the verse. If it had said that then it would mean loving the other person and that would mean that we would be obligated to equate the love of the other with the love of ourselves. Such a task is simply impossible to accomplish. Rather the love expressed here is an obligation in relations to all other people. In contrast the love which is directed to the person of the other requires fulfillment of certain conditions which happens only extremely rarely. It requires a high degree of compatibility and closeness between the souls which is found only between a few people for example Dovid and Yonason. Concerning their love it says, “The soul of Yonason was bound with the soul of Dovid and he loved Dovid as his own soul. (Shmuel I 18:1). In contrast it says here, “And you shall love your fellow as yourself.” The term “your fellow” does not mean the unique person of the other but merely the fact that he is human. Therefore you should do what you can regarding the conditions of his life that they be good or improved and that is what our love is directed at. In sum the verse is commanding us to be concerned about his welfare and what is good for him in the same way we are concerned that we obtain good things in our lives [but does not require that we love him personally]. We should be happy with his wealth and said with his suffering – as if these had happened to us. With generosity we should contribute to his well-being as if it was our own well-being and we should protect him from suffering as if the harm was a threat to us. This requirement can be done in regards to all men – even if you don’t feel any personal closeness to them. That is because this mitzva is totally detached from any personal feelings to the other person and is not based on any personality characteristics he possesses. The whole basis for being concerned about others is because of the phrase “I am G‑d” that ends this verse. G‑d has obligated us to relate in a positive fashion to all men because He has established that we all are “comrades” with each other. Comradeship increases his welfare and with the welfare of your fellow brings genuine peace. Such an attitude prevents us from being bothered by the success of others and the success of one does not come at the destruction of another. A person doesn’t rejoice in his own success as long as he is aware that his fellow is suffering.