According to the teachings, you wouldn't be here if you hadn't performed good Kamma in the past. You have beneficial opportunities in your life due to having performed good actions in the past, that's the importance of producing good Kamma. On a moment-to-moment level, if you want more happiness in your life you have to understand the causes of happiness and sow them. From your investigation into the mind, you see that if you think beneficial thoughts you have the beneficial result of the fading away of Dukkha. If you think harmful thoughts, than you have Dukkha arising in the mind and in the body.
So this Law of Cause and Effect governs our existence in this world. If we want benefit, if we want happiness, we have to sow the causes, if we want to avoid suffering through Compassion to ourselves, we sow beneficial causes. And if you have learned to reflect on your good Kamma, then you see that it helps produce happiness and confidence. Confidence in our ability to do more good actions and develop spiritual happiness.