Man thinks to himself: Why need I trouble about what happens in the spiritual world? When I die I go into the spiritual world in any case and then I shall see and hear what goes on there! In endless variations one hears this easy-going way of talking: Why should I trouble about the spiritual before I die? When the time comes I shall see what there is to see. My relationship to the spiritual world will not be altered in the slightest, no matter whether I do or do not concern myself with it. — But indeed this is not so! A man who thinks in such a way will enter a world of darkness and gloom, unable to make very much of what is said in my book Theosophy about the spiritual worlds. For it is only by allying himself in spirit and soul with the spiritual world during life in the physical world that man can acquire the faculty of perception in the spiritual world; the preparation must be made in his life here on earth. The spiritual world is there in very truth — the faculty of being able to see in that world must be acquired on the earth; otherwise there is blindness in the spiritual world.
Source: Rudolf Steiner – GA 107 – The Deed of Christ and the Opposing Spiritual Powers – Berlin, 22nd March 1909