If you want to know other person, first you have to know thyself.
If you want to be happy, first you need to make other person happy.
If you want to empathy with someone, first you should experience what you would feel in someone situation.
If you love somebody, hurting him hurts you even more.
Giving don’t means depleting oneself of something. You can gave something to other person, and at the same time receiving something else without loosing anything. Multiplaying resources, similiar as what Jesus did multiplying bread and fish among people.
In this sense, egoism is a virtue – you have to be egotistic to be truly empathic.