What is the speaker's attitude about the ride in the first three stanzas?

In "Because I Could Not Stop for Death," perhaps one of Emily Dickinson's most-read and discussed poems, a clear tonal shift exists between the first three stanzas of the poem and the final three. One possible interpretation of the poem as a whole is that it represents the speaker's slow realization that she has died—and her ultimate acceptance and understanding of it. 

The speaker's attitude in the first three stanzas can be seen as polite, but distant. The speaker appears to be someone who was very caught up in whatever constituted her day-to-day life. The poem's opening line, "because I could not stop for death," and her setting aside "my labor and my leisure" indicate a preoccupation for activity—and are a sharp contrast to Death, who "knew no haste." As anyone who gets a rare day off after going nonstop for a few weeks can attest, that first moment when there's nothing to do but quietly relax can be a little bit jarring. The speaker appears preoccupied, but willing to pause for this carriage ride.

The speaker doesn't appear to mind the break from her life either. In referring to death, she is very polite, saying "He kindly stopped for me" and that she put aside what she was doing "For His Civility." In the first three stanzas at least, she doesn't appear to be concerned that she's sharing a carriage with Death, her host, and Immortality, the other silent passenger on this ride. While it could be that she's merely being polite, there is also no indication that her politeness is masking any other conflicting emotions.

While the third stanza shows only action as the travelers pass a school, fields, and the setting sun, this action still offers insight into the speaker's perspective and what she is choosing to recall. For most, all these images elicit fond positive imagery: childhood, abundant crops, and the sun are all associated with life and vitality. She may be on a leisurely ride with Death, but her perspective is still concerned with the world of the living, of youth, vibrance, and abundance.

Because of this, it could be argued that the meaning—or perhaps permanence—of her carriage ride is still lost on her. From her perspective, she could still depart the carriage at any moment, rejoin the living, and get back to her daily rituals.

This initial perspective is driven home in the fourth stanza, when it becomes apparent that although she had been willing to entertain Death on this journey, she was not expecting it to be taking her to her "final destination," so to speak. Too late, she realizes that the sun is setting (a common metaphor for dying), and judging by her attire ("For only Gossamer, my Gown— / My Tippet—only Tulle"), she had not been prepared. 

The rest of the poem finishes drives this point home as the reader learns the speaker has been dead for centuries. This, coupled with the seemingly naive indulgence of Death in the first three stanza, seems to imply that perhaps no one is ever really prepared to die, and that death's finality can—either figuratively or literally, depending on one's view of the afterlife—take much longer than one's own lifetime to accept.