External factors may contribute to your happiness, but they are not the fundamental source of happiness. True happiness originates in the individual's mind. Your own happiness is related to others. If you love others, and never do harm to others, you will have happiness. On the other hand, if you neglect or don't care for others' happiness, you won't have happiness, for we are all interdependent. Your happiness or suffering depends on others' happiness or suffering.
We are lucky to be humans, for only humans have the most wonderful intelligence, compared with other mammals or living beings on earth. But if humans use their intelligence only to satisfy their desire, or immerse themselves in greed, hatred and anger, and only want to harm others, then they just waste their lives. Since birth, we have owed our life and survival to many other beings, so, if we use this life only to cause harm to others, then it would be better had we not been born into the world as humans at all.
Besides, the law of cause and effect is always in action at the micro as well as the macro level. Those who sow the winds and cause harm to others, sooner or later, in due time and with the right conditions, will reap the whirl wind, and get harmed in one way or another.
That's why Buddhists are vigilant about their thought, speech and action.
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