How we cite our quotes:
Every young lady may feel for my heroine in this critical moment, for every young lady has at some time or other known the same agitation. All have been, or at least all have believed themselves to be, in danger from the pursuit of some one whom they wished to avoid; and all have been anxious for the attention of some one whom they wished to please. (10.21)
Catherine finds herself in a love triangle here, a universally understood situation. Given how many ludicrous situations Catherine finds herself in, it is notable that this one is so common. She is pursued by John Thorpe and longs for the attention of Henry.
"You will allow that in both [marriage and dancing], man has the advantage of choice, women only the power of refusal; that in both it is an engagement between man and woman, formed for the advantage of each; and that when once entered into, they belong exclusively to each other till the moment of its dissolution; that it is their duty, each to endeavour to give the other no cause for wishing that he or she had bestowed themselves elsewhere." (10.53)
Henry makes a surprisingly good analogy, or comparison, between marriage and dancing, both of which have certain obligations aside from two people simply loving one another.
"But so it always is with me; the first moment settles every thing. The very first day that Morland came to us last Christmas - the very first moment I beheld him - my heart was irrecoverably gone." (15.12)
Isabella promotes a doctrine of love at first sight here. Given that this is coming from Isabella, these assertions might not be very true. Isabella is greedy, so her idea of love at first sight probably has more to do with money than love.