It is very important to generate a good attitude, a good heart, as much as possible. From this, happiness in both the short term and the long term for both yourself and others will come.

The Dalai Lama

For realzies

I believe all suffering is caused by ignorance. People inflict pain on others in the selfish pursuit of their happiness or satisfaction. Yet true happiness comes from a sense of inner peace and contentment, which in turn must be achieved through the cultivation of altruism, of love and compassion and elimination of ignorance, selfishness and greed.

~The Dalai Lama