Reading the letters day by day insofar as the novel will permit--and epistolary narrative as practiced by Richardson will not let us do this in any consistent manner--brings out the slowly revolving and changing phases of Lovelace's and Clarissa's relationship. Caroline Brashears' has shown us further how Richardson uses his slowing down of and games with time and letter to reveal how Lovelace and Clarissa construct one another (of Richardson wouldn't use this verb) how Richardson gradually and in a serpentine way (the favored line of the period wasn't it?) develops the direct parallel between Lovelace and James at this point
I just read the texts labelled Sunday, April 16th (from the second section of Letter 121, labelled Sunday morning, Ross, Penguin, p 454, and stopped as soon as I came to a Monday April 17th (Ross, Penguin, p 462). This took me from the 5th paragraph of Letter 121 through to but not including Letter 126. In these letters "in continuation" (wonderful phrase that, continuous memory and imagination interwoven is what it means) Clarissa also examines Lovelace and in her descriptions of him we see he is examining her response to his responses. There is such a preternatural alertness about them you'd think they'd get exhausted after five minutes of this, but, no, they are tireless, and immediately after they go directly upstairs or wherever their rooms are to examine and think it out some more.
The thematic point I'd make tonight is that by just reading this tiny series we get a sense of Clarissa calming down a bit, she's not flaring up so quickly, she's beginning to believe Lovelace and when she sees the believable letters and listens to him speak in sensible decent ways, far more kindly on the surface after all than anyone has been for what seems weeks and weeks she's grows a bit more willing to believe in him than before. We hear him through her, and though we can interpret his words somewhat differently they are heard through her ears at this moment; his letters for Friday suggest he too is beginning even to like Clarissa or at least respond to his respect for her; he seems less histrionic when he ends: "For myself, I have as good motions, and perhaps have them as frequently as anybody all the business is, they don't hold; or, to speak more in character, I don't take the care some do to conceal my lapses."
But this is wrong or partial. Because peeking ahead to the next page, tomorrow's reading, and skimming (I have read the book before), Monday morning, April 27 Let 126 by Clarissa (Ross Penguin, pp 462-3), & then Saturday, Sunday, and Monday, all Leter 127 by Lovelace (Ross Penguin, pp 463-5), but stopping faithfully at Let 128 as this is labelled Tuesday, April 18, I gather while Clarissa was feeling momentary peace or a sense of gaining some reins on her situation and reality, he was exulting, plotting revenge, barely containing a malignity which is parallel to that he accuses Clarissa's family of, and after all, he has no real reason to be enraged with her beyond that she is not in love with him, but only willing to become in love if he behaves in a way that will make her love him. He tricked her, not she him, and so on.
I wonder if Richardson was aware of what the effect of reading strict diurnal separations of his text could lead to. I doubt he meant us to. Calendar time is a device of novelistic verisimilitude and Richardson was ready to sacrifice that surface need in the deeper patterning of his novels all the time, as he says, "continually."