Quote 1
"My situation in life, my connections with the family of de Bourgh, and my relationship to your own, are circumstances highly in my favour; and you should take it into further consideration, that in spite of your manifold attractions, it is by no means certain that another offer of marriage may ever be made you. Your portion is unhappily so small that it will in all likelihood undo the effects of your loveliness and amiable qualifications. As I must therefore conclude that you are not serious in your rejection of me, I shall choose to attribute it to your wish of increasing my love by suspense, according to the usual practice of elegant females." (19.17)
It is literally impossible for us to understand why Mr. Collins' helpful pro-con list didn't convince Lizzy to marry him immediately.
Quote 2
"Pardon me for interrupting you, madam," cried Mr. Collins; "but if she is really headstrong and foolish, I know not whether she would altogether be a very desirable wife to a man in my situation, who naturally looks for happiness in the marriage state. If therefore she actually persists in rejecting my suit, perhaps it were better not to force her into accepting me, because if liable to such defects of temper, she could not contribute much to my felicity." (20.4)
Notice how it's all about Mr. Collins' felicity, and not about his prospective wife's? Yeah. Good luck with that, Charlotte.
Quote 3
"The death of your daughter would have been a blessing in comparison of this. […] Howsoever that may be, you are grievously to be pitied; in which opinion I am not only joined by Mrs. Collins, but likewise by Lady Catherine and her daughter, to whom I have related the affair. They agree with me in apprehending that this false step in one daughter will be injurious to the fortunes of all the others; for who, as Lady Catherine herself condescendingly says, will connect themselves with such a family?" (48.11)
When so much revolves around class status, what one person does affects the whole family. When Lydia runs off, she actually casts shame on her sisters. (If you're thinking that this sounds a lot like high school, we… kind of agree with you.)