I will try at some juncture to say my own bit here, but for now let me say that this is one of the most inspiring quotes about relationship that I have ever come across and I highly recommend this work. There are chapters and chapters of these brilliant and soulful observations in the book, which is ridiculously worth reading (as are most Rilke writings…)

         “…They hurry to a conclusion; to come, as they believe, to a final decision, they try once and for all to establish their relationship, whose surprising changes have frightened them, in order to remain the same now and *forever* (as they say). That is only the last error in a chain of errings linked fast to one another. What is dead cannot even be clung to (for it crumbles and changes its character); how much less can what is living and alive be treated definitively, once and for all. Self-transformation is precisely what life is, and human relationships, which are an extract of life, are the most changeable of all, rising and falling from minute to minute, and lovers are those in whose relationship and contact no one moment resembles another. People between whom nothing is accustomed, nothing that has already been present before ever takes place, but many new, unexpected, unprecedented things. There are such relationships which must be a very great, almost unbearable happiness, but they can only occur between very rich natures and between those who, each for himself, are richly ordered and composed; they can united only two wide, deep, individual worlds. –Young people–it is obvious– cannot achieve such a relationship, but they can, if they understand their life properly, grow up to such happiness and prepare themselves for it. They must not forget, when they love, that they are beginners, bunglers of life, apprentices in love, –must *learn* love, and that (like *all* learning) wants peace, patience, and composure! 
To take love seriously and to bear and learn it like a task, this it is that young people need. — Like so much else, people have so misunderstood the place of love in life, they have made it into play and pleasure because they thought that play and pleasure were more blissful than work; but there is nothing happier than work, and love, just because it is the extreme happiness, can be nothing else but work. So whoever loves must try to act as if he had a great work: he must be much alone and go into himself and collect himself and hold fast to himself; he must work; he must become something! For believe me, the more one is, the richer is all that one experiences. And whoever wants to have a deep love in his life must collect and save for it and gather honey.’ “

Find more on Rilke and links here and here.