Many couples in love are unaware that their happiness - it is a gift of nature, presented only for procreation. It is natural, "biochemical" love in a short time makes two absolutely strangers not only family, but also necessary to each other, as the air. Negative experiences as lovers arise from the social problems, discrepancies.
Familiarity with the physiological basis of love, you can start with the fact that the choice of the object of attraction occurs at the genetic level, ie more than humans differ from each other, the stronger their attraction to each other. This is due to the fact that these kinds of people are more healthy and adapted children. While not always a biochemical process runs simultaneously in both, then the person has mixed feelings of happiness and sorrow, the so-called unrequited love. To survive it, he needs time, distance and control their own feelings. If the spark jumps between the two at the same time, then people fills a sense of boundless happiness - the euphoria of love.
Based on natural love - the instinct of procreation - often makes male achieve favorite female at any cost, fighting with other contenders. Although in the human world is that females are fighting for the male.
Selecting a pair of Natural instincts guarantees only good offspring. But this love does not promise 100% family happiness, love and fidelity. On the contrary, people socially than closer to each other, and the closer they are genetically well to best progeny genes should be maximally different. If a couple are close, related genes, it can adversely affect the offspring in a variety of diseases and deformities.
"Shelf life" of the natural love small - one - two years. After the end of the instinctive love may continue married, if properly maintained and nourished, then over the years, it will become only stronger. If the natural love does not grow into a deeper, then soon enough sexual instinct will only alienate the spouses from each other. This will cause a desire to look for a new loved one, often only a new sexual partner.