Ultimately, the reason why love and compassion bring the greatest happiness is simply that our nature cherishes them above all else. The need for love lies at the very foundation of human existence.
An important distinction can be made between religion and spirituality. Religion [is] concerned with faith in the claims to salvation of one faith tradition... Spirituality is concerned with qualities of the human spirit, love and compassion, patience, tolerance, forgiveness, contentment, a sense of responsibility, a sense of harmony, that bring happiness both to self.
I think there is a complicated side effect to overcoming evil in that we are forever changed by it. I think after we ingest some of the cruelty of the world, it takes years off of our lives, but it also gives us wisdom and a little grace, hopefully a sense of compassion.
Supreme good is like water. Water greatly benefits all things, without conflict. It flows through places that people loathe. Thereby it is close to the Way.
For fear of causing terror to living beings, Mahamati, let the Bodhisattva who is disciplining himself to attain compassion, refrain from eating flesh.