Why Does Darcy Begin His First Proposal To Elizabeth By Saying In Vain Have I Struggled?

Mr. Darcy’s introduction before his fateful first proposal involves him inquiring about Elizabeth's health, Mr. Darcy then nervously paces around the room for a few minutes, this may serve of evidence of an internal battle between his love and admiration for Elizabeth and contemporary societal beliefs that would prevent him from confessing such feelings. This is evidenced later in the chapter during Darcy’s speech when he references her connections. Mr. Darcy says that 'perhaps these offences could have been overlooked, if your pride had not been hurt by my honest confession of scruples which had prevented me from forming a serious conception for a long time'. This explains why he believes his honesty made her reject him and asks her: 'Can you expect me to rejoice in the inferiority of your connections?'. This statement further emphasises how much Darcey has changed at the end of the novel in pride and demeanour. After what seems like much internal debate suddenly, he declares his love for her. He starts by eloquently expressing his admiration. He then refers to the inferiority of Elizabeth's social connections and explains that her family's rather unattractive behaviour dissuaded him from proposing sooner. He says, “In vain have I struggled. It will not do. My feelings will not be repressed. You must allow me to tell you how ardently I admire and love you”. Darcy allows his pride to guide him. In his proposal to Elizabeth, he spends more time emphasizing Elizabeth’s lower rank than actually asking her to marry him (“he was not more eloquent on the subject of tenderness than of pride”).
Elizabeth is absolutely baffled. She replies with, “...or had [my feelings] even been favourable, do you think that any consideration would tempt me to accept the man, who has been the means of ruining, perhaps for ever, the happiness of a most beloved sister”? Elizabeth, it seems, only declines him out of disgust because of what he’s done against her sister.