In our life we may meet someone with whom we feel that a good friendship may be built up and shall never say goodbye.
If the friendship is between man to man, it is possible that the friendship will last forever, but if the friendship is between man and woman, the situation may be different at end.
It is human nature that man and woman can only be a friend for a short time. If a man and a woman have friendship for a long time, unless the friendship can turn to love, they will be separated suddenly without any warning of sentiment feeling beforehand.
It will be, of course, sad to have goodbye without saying goodbye. Why man and woman cannot have friendship, it is because they have nothing in common to talk with. But, if they have love, they can talk anything, even meaninglessly, and still feel enjoyable.
In the example of history, only the friendship between man to man can last forever, but never happen between man and woman unless they have love.
To conclude, only love can make man and woman together forever. Without love man and woman must live their life in their own field. It is the nature of human.
Up to now, there is no writer, writing a book about love and how to handle love in a proper way. Philosopher Nietzsche said: “A woman may very well form a friendship with a man, but for this to endure, it must be assisted by a little physical antipathy.”