The greater ability for experiencing abstract and general feelings, that is feelings that are only the consciousness of what several individual feelings have in common, like the greater ability for forming abstract and general ideas is the greatest distinction of hearts and minds. Only those hearts capable of such feelings are truly just, for it is only them that are capable of being ruled by immutable principles. Only on the sensibility of such hearts can we rely, as they are always susceptible to being moved by general motives. Their conscience is silenced with difficulty – and it is always active. Remorse is in them less fallible and more efficacious, all the ideas of its duties more complete. Such people especially know to fulfill these delicate duties of honesty that morality alone imposes and recognizes, and which always bring regret and the loss of feelings of happiness when they are forgotten, and which display those disinterested virtues, the fruit of a sublime need to have always the greatest and most satisfying idea of oneself.--Sophie de Grouchy (1798) Letters on Sympathy, translated by Sandrine Berges, Letter 5.
ln the quoted passage, De Grouchy embraces the idea that various exalted cognitive and intellectual abilities are prerequisites to, let's call it, exemplary moral behavior (in which she includes acting from principle in light of conscience and the right sort of feelings and impartial motives). Having an 'active' conscience means it can motivate action. Now, I think that with 'honesty,' De Grouchy is evoking Cicero's honestum (from De Officiis), or that what is honorable or noble.
Unfortunately, it is not entirely obvious how early moderns understood Cicero's honestum. In a classic article, James Moore, has canvassed eighteenth century (primarily British) attempts to articulate it in a modern context. On Moore's reading, by the time of Hume, honestum is grounded in the sentiment of humanity. De Grouchy is not a critic of the sentiment of humanity; she treats it, for example, as the "first cause" of sympathy (in Letter 1). But in the quoted passage she suggests that morally exemplary behavior is psychologically grounded ultimately in a peculiar form of self-love: "the fruit of a sublime need to have always the greatest and most satisfying idea of oneself."
De Grouchy seems here to be offering the wrong sort of reason to explain exemplary acts of honor, and to be swerving uncomfortably close to those unmasking masters of morality -- Mandeville, Nietzsche, etc. -- who suggest that moral behavior is just another species of self-love or vanity. Now, to be sure, De Grouchy is clearly not suggesting that we act good because we desire praise or to be thought well by others. So, she is not charging the moralist with hypocrisy or a certain form outer-directed dissembling. And, in addition, she is suggesting that moral actions are done for properly moral reasons (i.e., principles).
Yet, the psychological cause of exemplary moral behavior is the desire to have the best possible and most gratifying self-image and to live up to it. It's this need that is called 'sublime' by De Grouchy. I think on this point De Grouchy echoes two famous predecessors--one of which she certainly read. First, she evokes Spinoza's idea from the preface of Ethics 4, that "because we desire to form an idea of man, as a model of human nature which we may look to...I shall understand by good what we know certainly is a means by which we may approach nearer and nearer to the model of human nature that we set before ourselves." As Andrew Youpa has suggested, this exemplary idea is both adequate and inadequate in Spinoza. In its adequate manifestation it is an expression of God and this connects up to the De Grouchy's sublime.
Undoubtedly, the previous paragraph is rather too speculative for most. Not only because De Grouchy does not often hint of Spinozistic influence, but also because she is herself rather allergic of talk of even Spinoza's God. So, it is more likely that she is articulating an idea she found in The Theory of Moral Sentiments (hereafter TMS, which she translated and to which her Letters are an appendix). There Smith denies that our morally exemplary behavior is caused by "the love of our neighbour," as the Christian hopes (and Hutcheson thought) nor is it "the love of mankind," (which the defenders of humanity had promoted), rather it is a stronger love, a more powerful affection, which generally takes place upon such occasions; the love of what is honourable and noble, of the grandeur, and dignity, and superiority of our own characters" (TMS 3.3.4).
It is not entirely clear if Smith here offers two distinct strong motives that can explain (most) exemplary moral behavior: one is love of the noble (that is, a desire to be Cicero's honestum) and the other is very close to De Grouchy's posited desire to live up to the best possible and most gratifying (exalted) self-image, or that these amount to the same thing. Either way, both De Grouchy and Smith assume (with the Stoics) that what we think of ourselves will influence our behavior and that we better have access to rather inflated ideas (of the right sort) of ourselves in order to act nobly when needed such that the inflated idea becomes a self-fulfilling prophecy.