May my story be a warning to all, how they prefer a libertine to a man of true honour; and how they permit themselves to be misled (where they mean the best) by the specious yet foolish hope of subduing riveted habits, and as I may say of altering natures! — The more foolish, as experience might convince us, that there is hardly one in ten of even tolerably happy marriages, in which the wife keeps the hold in the husband‘s affections which she had in the lover‘s. What influence then can she hope to have over the morals of an avowed libertine, who marries perhaps for conveniency, who despises the tie, and whom, it is too probable, nothing but old age, or sickness, or disease (the consequence of ruinous riot) can reclaim?
It seems to have taken a long time for Clarissa to come to this view: that her story is a “warning” to other women. Her family has made similar remarks. This stance seems rare, though: how might this letter suggest personal blame? In death, does she see herself as a martyr?
Clarissa seems to be taking the blame for everything that has happened to her. It is very possible she sees herself as a martyr because she very deliberately says “May my story be a warning to all.” Clarissa clearly liked Lovelace and obviously preferred him to Solmes and the other potential men that came to court her. Being the good virtuous Clarissa she is, she has turned her sad life around to be a warning to girls to not be carried away by a lover/rake but instead to “give the weight [women] ought to give to the qualities of sobriety and regularity of life and manners in [men].” Rather than blame Lovelace for tricking her, Clarissa takes the blame of how her life has turned out and notes that only one in ten marriages are happy and that a woman cannot hope to truly reform a libertine. So Clarissa is preparing herself for matyrdom and possibly securing herself against any criticism that could arise from Lovelace or whomever.
It also seems to me that in seeing her story as a “warning,” she's discovering the limits of the view from virtue: even a woman conscious of the nature and need of virtue, and setting out with the best of intentions, may be deceived (either by her own sense of strength or her lack of worldly knowledge) and come to ruin. When I first encountered this idea of self-blame, it struck me as–to be Lovelace for a second–overly “nice.” But I'm seeing it more and more as a recognition of necessary but limited responsibility. She's still sharp enough to comment on the roles of her own family, and of Lovelace, in the worst that has happened to her; but in her more thoughtful and more informed understanding of the world, and of how she lives and moves in it, she can more thoughtfully assign herself responsibility–but not, I think (nor should she) real blame.
This idea that her story can be a lesson has been floated before by Anna. Also, she has previously said on a number of occasions that she was over-proud in her belief that she could change Lovelace. I don't think this is self-blame. But I do think she now understands things she earlier did not. Also, for Richardson, this was one of the most important take-aways from the novel: rakes do not make good husbands, reformed or not.
This read to me a lot like Richardson speaking through Clarissa as well, but to follow up on the blame thread, I think it's possible for Clarissa to acknowledge the sin of pride without taking full responsibility for everything that's happened to her. She, by her own characterization, was “foolish” yes, but she “permit[ted]” herself to be “misled.” There are two responsible parties here, Clarissa for permitting Lovelace to write her at all, but also Lovelace for willfully deceiving her. I think it's a both/and proposition that nicely allows for her to think of herself as having some agency in the events of the last few months, without condemning herself too much for Lovelace's actions. A nice balance.