The word in the New Testament that we translate "kingdom"--as in Kingdom of God--is interesting in that it is not a reference to the realm (the place, the geography, the property), but to the rule. That is, those who have the Kingdom of God--as in "theirs is the Kingdom of God"--are those who are ruled by God. That is the blessing of the Beatitudes: to be ruled by God.
On the one hand, that's pretty heady stuff, to be ruled by God; yet on the other hand it is something we all already know. God rules everything. All the physical, biological and psychological laws that rule our life, rules that we know already, rules that no one escapes from, these are all manifestations of God's rule in our life--even if since the 18th century we have preferred to ignore God and deify the creature, as if law and matter were eternal. Despite our protestation, this is still God's rule.
Within this rule, we can either cooperate and transcend even what seem to be our limits, or we can fight and rebel and destroy ourselves imagining that the universe as we would like it to be will somehow save us from the universe as it is. For example, mankind is limited by the rule of God as it is manifest in this physical reality, so we walk the earth and watch the birds fly. However, by careful attention, one can learn to cooperate with the rule of God. One can learn to fly.
More than a millennium before the word "science" came to refer exclusively to what used to be called natural science, holy men and women talked about the science of the spiritual life. I'm not referring to metaphysics. I am referring to the practice of paying attention to one's inner life, one's relationship with God. Through attention, one can cooperate with the rule of God in the heart/mind and transcend, or rather be transfigured beyond what were thought to be the limits of a merely human existence.
This transfiguration begins by learning and cooperating with the laws of God's rule, laws that have both been revealed and discovered. And herein lies the rub. Unlike some of the other laws of God's rule that can be manipulated to selfish and destructive ends--the science of flight, for example, has advanced principally spurred by the desire to exploit its military and commercial possibilities--spiritual laws deal with the healing of our sinful and selfish hearts, our inner selves, our selves hidden behind the mental fig leaves that we sew for ourselves. The beginning of our transformation, of our cooperation with God's rule in our hearts/minds, is a changing of our mind and heart called repentance. Repentance is the intentional cooperation with God in the heart.
Just as physical flight did not begin with rockets, so repentance does not begin with unceasing prayer. Flight began by paying attention to the wind, by observing what ascends (hot air) and what doesn't. Similarly, our repentance begins with attention to the Wind of God, the Holy Spirit. Where does it blow? How can I move with it? What in my thoughts or actions "quench" it's movement? What encourages my thoughts to ascend towards God? What drags them down to the replaying of mental videos of futility? Many of the laws for the spiritual life have been revealed, but until one applies them, they are only words. Those who have flown before us have left us instructions, advice on how to begin. Basil the Great left us this:
"How are we to come to this humility and leave behind us the deadly swelling of arrogance? By exercising ourselves in it in all things, and by keeping in mind that there is nothing which cannot be a danger to us. For the soul becomes like the things to which it gives itself, and takes the character and appearance of what it does."
"Let your demeanour, your dress, your walking, your sitting down, the nature of your food, the quality of your being, your house and what it contains, aim at simplicity. And let your speech, your singing, your manner with your neighbour, let these things also be in accord with humility rather than with vanity. In your words let there be no empty pretence, in your singing no excess sweetness, in conversation be not ponderous or overbearing. In everything refrain from seeking to appear important. Be a help to your friends, kind to the ones with whom you live, gentle to your servant, patient with those who are troublesome, loving towards the lowly, comforting those in trouble, visiting those in affliction, never despising anyone, gracious in friendship, cheerful in answering others, courteous, approachable to everyone, never speaking your own praises, nor getting others to speak of them, never taking part in unbecoming conversations, and concealing where you may whatever gifts you posses."
There's a start.
(Quote from St. Basil the Great, Homily on Humility, 20 as found in Kyriaki and Thomas FitzGerald's book, Living the Beatitudes.)