What would be 3 or 4 good quotes that I could include in a paper on the topic of grace (last chapter) in the book "The Road Less Traveled" by Scott Peck? Can you also please explain the quotes?

In his introduction to this final section of the book, Peck sets out his key theses on the topic of grace: it is something which amazes us, and it is actually a "common phenomenon"—just one to which we pay little attention. Peck explains:

Something amazes us when it is not in the ordinary course of things, when it is not predictable by what we know of "natural law." What follows will demonstrate grace to be a common phenomenon and, to a certain extent, a predictable one. But the reality of grace will remain unexplainable within the conceptual framework of conventional science and "natural law" as we understand it.

This quotation summarizes how Peck approaches the idea of grace. He believes grace to be readily found among us but that this does not diminish its miraculous nature. He also identifies "conventional science" as being unable either to recognize or to admit the existence of grace, something which actually leads us to question the stability of those who are actually "amazingly healthy mentally." Peck goes on to point out that psychiatry, too, is an inexact science, yet those who expect psychiatry to explain everything still do not admit the existence of grace. Grace is, according to Peck, "a force, the mechanics of which we do not fully understand, that seems to operate routinely in most people to protect and to foster their mental health even under the most adverse conditions." When psychiatry and conventional science cannot assist or explain, grace intervenes.
Later, Peck questions the idea of humans being "accident resistant" and whether this too is evidence of grace. He asks,

Could it really be that the line in the song is true: "Tis grace hath brought me safe thus far"?

This is an important quotation because it forces the reader to confront his or her own prejudices about the balance of the universe and what maintains that balance. Peck allows that many mainstream scientists will describe this as a "manifestation of the survival instinct," but, Peck says this is not an explanation of the phenomenon. Naming this tendency in humans does not explicate why the instinct exists. Instincts of this kind, Peck emphasizes, are actually manifestations of this force we do not understand: grace.
Peck explains how the "scientific" person still chooses to interpret the machinations of grace in unscientific ways:

The reader may choose to assign the mystery of such incidents to "pure chance," an unexplainable "quirk" or a "twist of fate" and be satisfied thus to close the door on further exploration. If we are to examine such incidents further, however, our concept of an instinct to explain them is not terribly satisfactory. Does the inanimate machinery of a motor vehicle possess an instinct to collapse itself in just such a manner as to preserve the contours of the human body within? Or does the human being possess an instinct at the moment of impact to conform his contours to the pattern of the collapsing machinery? Such questions seem inherently absurd.

The "rational" explanation for whatever it is that protects us from harm, Peck says here, is actually no more rational than the idea that a miraculous force, "grace," is at work.
Drawing upon his psychiatric experience, Peck focuses in this chapter upon the truth of the unconscious, that unexplained part of ourselves that can be said to constitute our true self. Peck says:

We are always either less or more competent than we believe ourselves to be. The unconscious, however, knows who we really are. A major and essential task in the process of one's spiritual development is the continuous work of bringing one's conscious self-concept into progressively greater congruence with reality.

According to Peck, when a person actually achieves this synchronicity between their belief of themselves and the truth of themselves, they experience a sense of having been, as in the song "Amazing Grace," blind while now finally being able to see. This feels like a miracle. But, in fact, it is simply that most of us go through life with a discord between the truth of ourselves and the way we perceive ourselves to be. According to Peck's philosophy, the "grace" achieved through bringing these two selves together is both miraculous and also completely ordinary. Peck believes that we are all capable of achieving this miracle and that science is capable of, to an extent, understanding it. However, this does not diminish the impact it has on our lives or the extent to which it feels like something divine and incredible.