According to the site The Life of Jesus in Chronological Order timeline, the Sermon on the Mount was given in April, 27 A.D.. Jesus had been preaching around Galilee since September, 25 A.D. and appears to have had his home base at Capernaum only a mile from the site of the Sermon on the Mount. In September, 27 A.D. he heads for Jerusalem about 120 miles south and is crucified in April 28 A.D..
If this timeline is correct Jesus’ ministry was only a year long after the Sermon, about six months while still near Capernaum and about seven months in transit and in Jerusalem. The time before the Sermon may be considered a preparatory period for his essential mission, and the events after it the development of the message. The Beatitudes are the steps on the ladder to heaven that he is explaining and illustrating during that short period.
By following the simplified version of his Golden Rule, “Everything others should do to you, do to them!”, and using the Beatitudes as the guide to things that should be done to others, we may ascend to Jesus’ heaven. By becoming skilled standing on each rung of the ladder of the Beatitudes to heaven we may reach for the next higher one. Because it is difficult, perhaps impossible, to simply tell our internal habitual selves to climb up this ladder, Jesus gives us an easier task. He recommends doing each of these beatitudes in order, from the bottom one to the top one, externally to others, where we can see them and do them intentionally. By doing each of these things externally to other people we develop the required habitual skills for doing them internally to ourselves.
Each of these actions is treating another person better than we treat ourselves. We are approaching a person that is mourning, from a state of our own desolation of spirit, and then mourning ourselves, and then from our state of mourning to comfort them. By doing that we learn to move from desolation to mourning and to give comfort. This is a skill that needs to be learned before you can successfully move up to the next rung on the ladder, that of being meek, and in that condition of giving the things that the earth is capable of providing. Going up these steps of the ladder may take some time and dedicated effort, but they are doable because they are individually easily done. Those things that people should do to you are to help you to attain your highest potential. You do that for other people by doing to them what they should do to you. Thus:
“Everything others should do to you, do to them!”