what's the purpose

But first, why are people (like me) angry with each other (like ... somebody else)?

Because "they" refuse to give what "one" wants. They choose to improve their own matters and to turn their back to one's problems. They chose to leave, and so to let one solve one's difficulties all alone. And one has a tone of problems.
They are supposed to have left having the best intentions, and the results are not among the best ones. What is one supposed to do now?
The first conclusion: Do something for yourself. Can you do that?
(to be continued).