What really is happiness?

Little by little they grew up and the girl showed him the best of the world and so they fell in love until they decided to date, they were in love, they were both scholars, the young man graduated and became a university professor, the girl graduated in management and they decided to get married, living together they overcame difficulties and hardships, until they managed to have a good life, rich and healthy, they had a very beautiful daughter and decided to teach her everything they know and went through, so that she is prepared for whatever comes, they taught her about the world and the people who live in it.

As if everything they've been through wasn't enough, he had to die to survive, could it be bad luck? Or is it another test that he has to pass until he is happy and without any sadness?