Begin to familiarize with the physiological basis of love can be that selective the object of attraction occurs at the genetic level, that is, roughly speaking, the greater the difference in the genetic codes of both the stronger mutual attraction since more than on the basis of the parents, the healthier and adaptable to their offspring (the principle of heterosis). It is not always this genetic 'trigger' starts the biochemical mechanism at the same time in both, there is a 'spark jumps between the two' – both figuratively talk about this love. But if it does, then necessarily there is a feeling of boundless happiness from a sense of oneness with the beloved person – reckless euphoria of love. Feelings, broke out just one, delivered him a double sense – 'mix' of happiness and sorrow. To survive this (unrequited love) takes time, distance and self-love to not become obsessive, eclipsing all desire – a schizophrenic 'obsession'. A Since the degree of self-control is individual and depends on the overall level of human development – from education, from the patterns of thinking and behavior, and this state is experienced differently. Moreover, the higher the level, the skilled man is able to control your instincts without harm to their own mental health, well – the physical health of others. By the way, often forcing people to seek you liked at any cost is not so much natural love as self-interest of the owner. Rather, the instinct of procreation, which is the basis of the natural love and jealousy and related natural competitive spirit makes men seek partner does not only because of the intimacy, but because of the desire to possess proprietary, and thus – away from rivals.