In this life, happiness or unhappiness is results of karma and karma is a truth

At this time, we have obtained a human body that has a human existence in this world. When we have the pleasant and unpleasant experiences of human beings we express different states of happiness and unhappiness. We are like children who wander through happiness and unhappiness, laughing and smiling one moment and crying the next. What is the cause of our happiness and unhappiness that change like the clouds in the sky? There are many ways to answer that question, but according to Buddha Śākyamuni we should recognize that these various states of happiness and unhappiness are results from good, bad, or neutral karma. If we analyze and investigate this answer correctly we will gain a profound understanding that is in accord with the true nature of things, and therefore this is something that everyone should seriously think about. It is important to do so because the path of correct reasoning brings us certainty.

 Hungkar Dorje Rinpoche, “Love and Peace“