It is important not to allow ourselves to be put off by the magnitude of others' suffering. The misery of millions is not a cause for pity. Rather it is a cause for compassion.
I do not perceive even one other thing, O monks, that when undeveloped and uncultivated entails such great suffering as the mind. The mind when undeveloped and uncultivated entails great suffering.
The rationale for loving others is the recognition of the simple fact that every living being has the same right to and the same desire for happiness, and not suffering, and the consideration that you as one individual are one life unit as compared with the mulititude of others in their ceaseless quest for happiness.