What need is there to say more?The childish work for their own benefit, The Buddhas work for the benefit of others. Just look at the difference between them. If I do not exchange my happiness, for the suffering of others, I shall not attain the state of Buddhahood. And even in Samsara I shall have no real joy. The source of all misery in the world lies in thinking of oneself; The source of all happiness lies in thinking of others.
Shantideva