The Baalei mussar say that it is harder to feel someone's simcha than to feel their pain. Very often people come to other's smachot just to be "yotzei" and run out early. "Gotta go". Some people have that rare quality to really FEEL and EXPERIENCE the simcha of others. As one who has made a number of smachot Baruch Hashem, I can tell you that it was those people who were really with me that made all the difference.