Why now is so much talk about weaning - when, what age, how?.. This is really a very important point.
Talk about the fact, as seen in psychoanalysis. At the beginning of development the child not yet distinguish between themselves and other people, the outside world. He rather sees everything through the prism of his sensations, and not even realizing that it is an inner feeling, but rather just perceiving them as comfortable, enjoyable and fun - and then what to do with them, too, is perceived as "good" or uncomfortable, generating displeasure - and then sootvetstvenno "bad" - that they will be associated.
When mom comes to feed the baby, gives him the chest, then the feeling of fullness, of warmth and satisfaction is perceived as associated with "good" breast, and when "breast" you have to call this "breast" feeding for too long, causing the feeling of overeating - then the chest becomes "bad". The baby still does not understand that it is one and the same chest, he just associates it with its current state. Gradually, the child gains experience when the "bad" breast (for example, mom was late, even for a few minutes on the call of a hungry child) became "good", and can expect that after the "bad" can come "good". But with all this he still remains at the stage when in fact mom is not a separate person, and it is a set of objects that deliver sensations of pleasure or displeasure (her breast, voice, gaze and so on), respectively, at a certain point in life (the first months) mother to child or totally "good" or totally "bad."
When mother takes the baby to the breast, the child gets the opportunity to see the mother (and to experience it bodily, physically) as another person, not like a breast that gives milk, but as another, separate person from himself and his intentions, deeds, interests, not always related with him.
it gives in the future? Understanding that in one and the same person can be combined and arbitrarily "bad" - that is experienced as bringing displeasure, and the "good" pleasurable feeling of the other individual in its entirety gives the opportunity to be in a relationship filled with different feelings, not only dichotomous "bad" - "good". Not only in "good" relationships, where there is only understanding, unity of values and attitudes, and not only the "bad enemy", but in such a relationship, where there is room for disagreements, misunderstandings, and a friend who is late for half an hour (a very conventional and simple example, and a situation of course, usually much more difficult) or making something that is experienced as unpleasant me - not deleted, becomes the person with whom the relationship further is impossible. For man becomes possible in the life of childhood friends - people with whom you can go through different situations, experience and common interests, and differences, a long-term relationship with someone who do not take the form of "swing" from idealization to devaluation.
In fact, weaning is the first loss in human life, which, paradoxically, becomes not a loss but an opportunity, an open door to finding a variety of sources to satisfy your "hunger", but not literally but symbolically - find friends, other people who can also give me pleasure (communication, interaction with them). And frustration here is much less, because when there is only one object that satisfies me (e.g., chest), I need to stay with him in the merger, and the lack of it brings much more discomfort than when I have different options and ways where you can have fun and meet their needs.