Collins came to Elizabeth in complete self assurance, and thinking he was THE best candidate for her. Keep in mind that Mr. Collins is the typical old-fashioned man who felt that he had reached the top of his life: A career in the clergy, a sponsorship by an aristocrat, and the Bennet's estate.
As a result, he thinks extremely highly of himself. In turn, he understood that this made Elizabeth a subject of his, who would love to accept a marriage proposal from someone of "his kind", and especially this would please Mrs. Bennet who would feel that she can keep the estate after Mr. Bennet is dead.
Unfortunately for Mr. Collins, he has a dull and subservient personality, he is obsessed with his aristocratic sponsor, Lady Catherine DeBourgh, and constantly speaks of her as part of his own collection of self-gratifying characteristics
However, Collins had another thing coming: Elizabeth was not at all impressed, and viewed him as a very minimal man. During the proposal, Collins over articulated, exaggerated, consistently brought up Lady Catherine, and basically placed Elizabeth in a role where he described her as someone who should be worthy of him. He suggested that her behavior was somewhat challenging, but hinted at his "fixing her" somehow, in not so many words.
As a result of Elizabeth's rejection, Collins was hit hard in the ego. He honestly could not believe it and he left ashamed, noticing how much more intelligent than he is, and this was something that, although was going to make Mrs Bennet LIVID, Elizabeth's sense of self was enough to make her feel good about what she did.
Collins proposes to Elizabeth on Wednesday November 27th at her own house (Ch.19). Collins is a cousin of Mr.Bennet who will inherit Mr.Bennet's estate after his death. This is why he is so arrogant and confident that Elizabeth will not reject his proposal. Collins takes Elizabeth for granted and impresses upon her that he is actually doing her a great favour by marrying her and tries to exploit her financial distress to his advantage. He does not care to find out leave alone respect her feelings with regard to marrying him.
He is completely unromantic. His arrogance prevents him from praising her beauty or her intelligence or flattering her before seeking her consent. Collins gives three general reasons why he wants to marry without specifying why he wants to marry Elizabeth in particular.
When he is straightaway rejected by Elizabeth, he thinks that she is only acting coy. Collins assumes wrongly that Elizabeth is only pretending that she does not like him and he tells Elizabeth,
"however your natural delicacy may lead you to dissemble"
Its a classic example of a situation of comical dramatic irony: the completely unromantic lout that Collins is he thinks that Elizabeth is pretending to be coy and hard to get!
A little later, after he has formally proposed to her and has been firmly rejected by Elizabeth he replies to her arrogantly and complacently in the following words:
``I am not now to learn,'' repliedMr.Collins with a formal wave of the hand, ``that it is usual with young ladies to reject the addresses of the man whom they secretly mean to accept, when he first applies for their favour; and that sometimes the refusal is repeated a second or even a third time. I am therefore by no means discouraged by what you have just said, and shall hope to lead you to the altar ere long.''
Once again, Collins assumes that Elizabeth is really attracted to him and wants to get married to him but that she is only playing hard to get and teasing him in the conventional manner of all young women.
However, Elizabeth firmly rejects him saying that she is not the conventional young lady who likes to be proposed to twice and that her rejection of him is final:
``your hope is rather an extraordinary one after my declaration. I do assure you that I am not one of those young ladies (if such young ladies there are) who are so daring as to risk their happiness on the chance of being asked a second time. I am perfectly serious in my refusal.
Even then Collins doesn't give up and remarks that when he next proposes to her she will accept him:
``When I do myself the honour of speaking to you next on this subject I shall hope to receive a more favourable answer than you have now given me;
To which Elizabet exasperatedly replies:
Do not consider me now as an elegant female intending to plague you, but as a rational creature speaking the truth from her heart.''
Finally the truth of the matter sinks into the thick headed Collins and he quits the place in deep embarrassment.
Elizabeth's refusal of Collins' proposal speaks volumes about her strength of character.