Specifically, the kingdom of God isn't a matter of becoming a good person. The kingdom of God is a matter of seeing. If you see clearly then the goodness--right action--follows as naturally as breathing.
An example of this is Thomas Merton's street corner revelation.
On March 18, 1958 Thomas Merton was in Louisville, KY for an appointment. Merton had been a cloistered monk for seventeen years. He had entered the monastery seeking an escape from the world so that he might draw closer to God. But on this day, standing on a street corner and watching the hustle and bustle of people, Merton had an experience of God that played an influential role in tuning him outward toward the world in the 60s.
Merton recounting his experience (from Conjectures of a Guilty Bystander):
In Louisville, at the corner of Fourth and Walnut, in the center of the shopping district, I was suddenly overwhelmed with the realization that I loved all those people, that they were mine and I theirs, that we could not be alien to one another even though we were total strangers. It was like waking from a dream of separateness, of spurious self-isolation in a special world, the world of renunciation and supposed holiness…A plaque marking the spot of this revelation (pictured above) can be found the corner Fourth and Walnut in Louisville.
This sense of liberation from an illusory difference was such a relief and such a joy to me that I almost laughed out loud…I have the immense joy of being man, a member of a race in which God Himself became incarnate. As if the sorrows and stupidities of the human condition could overwhelm me, now I realize what we all are. And if only everybody could realize this! But it cannot be explained. There is no way of telling people that they are all walking around shining like the sun.
Merton's revelation illustrates the point I'm making. Merton comes to see people with the eyes of God. We are all walking around shining like the sun. And upon seeing this, the illusion of separateness disappears and Merton's heart explodes: "I was suddenly overwhelmed with the realization that I loved all those people, that they were mine and I theirs, that we could not be alien to one another even though we were total strangers."
My observation here is that Merton doesn't, in this moment, need to try, through an act of will, to "be a good person." Instead, having come to see clearly, right action is easy and spontaneous.
The kingdom of God is learning to see what Merton saw that day on the corner of Fourth and Walnut.