Matthew 20 is quite unusual indeed. Like so much of what Christ says, it only makes sense from an inner point of view. This is because the inner point of view and the outer point of view are often at odds with one another.
There are many ways of saying this, and, as Cynthia Bourgeault's The Wisdom Jesus points out, we can't really understand Christ's teaching if we keep thinking of it as a literal or outer teaching. Yet in a certain sense, we can't understand Christ's teaching if we think about it, either. Because it is not just about thinking; one has to sense one's spiritual nature with the whole of one's being, through the roots of one's physical and sensory experience. This is an awkward enterprise without a real sensation of one's body; it always keeps the box locked. Thinking does not have a key with it; and the emotions are often equally confused. One must begin with an inner sensation of oneself, which is always and forever the first inkling of the presence of God, who is forever present in all Being.
This is particularly important to remember, not by reminding oneself in one's thought, but through the direct experience of life itself — the labor in the vineyard — within the organic sensation of being. It is here that God begins and where God's consciousness touches our own; and it is a subtle and beautiful thing indeed, which encompasses all truth. It is far more complex than the things that are said about it; and it extends its roots and tendrils not just into the crevices and cracks where good feeling and the warm compassion can be extracted, but into every crevice and crack, so that the wholeness of being, including both its goodness and badness (think of all the laborers in the vineyard) are present and accounted for. There is a distinguishing between the two; and it cannot be undertaken if one only goes towards the good. The wholeness of being includes all of the parts, even, yes, the ones whose eye is evil (see the parable.)
I bring this up not to try and encourage us to dwell on the bad, but to understand the wholeness. Understanding the wholeness involves residing within it, and not dwelling on the good or the bad. To dwell is to be stuck in a certain place; and where we need to dwell is in Being itself, not in the goodness and badness that accompany it. When we dwell in the goodness and the badness, we are inevitably stuck to them, one way or the other, as though they were glue.
It reminds me of the story of Brer rabbit and the tar baby; in the end, the way to get free of attachments lies through the thorns — which is, as it happens, where Being belongs in the first place.