This reflection is not about loving kindness. Loving kindness means making other people happy and this makes the doer feel as good or even better than the receiver. Imagine how wonderful the world would be if everyone is aware of this and starts to practice this. How could anyone criticize such a wonderful truth. Still people do criticize it
This reflection is also not about compassion. Compassion involves the relieving of pain.
This reflection is about sympathetic joy. This means being happy for the happiness of others. Even though most of would claim we have this, perhaps not many of us really can experience big joys for the happiness of others. We usually have something like, why not me, is he really happy, at what cost did she achieve this, how long will it last. For example do we feel really happy for those people who fly business class or first class if we fly economy? Looks like something more suitable for saints than normal earthlings like us. Yet with practice true sympathetic joy is possible. I will try it tonight.