If you are very new to Buddhism, you will not be very happy with my answers, for we are used to the "heavenly" promises from other religions. Buddhist interpretations of existence and the universe are totally different from other religions.
What is the basis of happiness? In common term, the basis of happiness is the presence of specific factors which make us happy. The most classic example will be having lots of money. Once this condition is present, the person will immediately feel a sense of happiness. After a certain period, this condition of just having money is no longer the main factor for his happiness. He will have to seek new factors to experience new happiness, like having a new house, new cars, and other things. Once these are fulfilled, the law of diminishing returns sets in. These conditions which previously generate lots of happiness are now stale. If no new conditions are satisfied, then the person will no longer experience the happiness again. In short, "happiness" is a "conditioned" experience. Without the prerequisite condition, happiness will not appear. The Buddha warned that all conditioned things are transient, they cannot last forever. Anyone who seeks or chases after happiness will be very disappointed in the end. However, this does not mean that a person should not be happy when conditions are right. The warning is that at any time these happy conditions may change. To an uninitiated person the absence of such happy conditions or the presence of negative conditions will trigger a state of unhappiness. The wise Buddhist approach to life is to be contented with the things we have, be happy when conditions are right, and be careful when conditions are not right. We have to ride through the waves of living conditions, the ups and the downs. In so doing, we live a guarded contented life.
Our place in the universe is just like a minute speck of dust existing for just a fraction of a blink of the eyes. If you go through a brief description on astronomy, you will know that the vastness of the universe is unimaginable; and the time frame is also beyond our reckoning. We are here because of the phenomenon of attachment. Just like a magnet, because of our ignorance to the real nature of our existence, we are bound by our desire to be attached to existence. This existence actually has no real benefit. The cycle of births and deaths keeps on repeating itself.