Karma (all thoughts, words, and deeds) that a person commits in this life becomes his future. In this life, a person receives the result of his actions (karma), committed not only in this life but also in the previous ones.
What does a given karma bad? It gives various torments, complexities, circumstances causing a person feelling bad. A good karma, on the contrary, gives everything that brings a person prosperity, and then his inner state and external circumstances of life are both good.