"It will pass."

[They are discussing the fact that Wickham has, in essence, extorted from them a fortune for the misery he is likely to face in marrying Lydia]

Mr. Bennet: I should have taken better care of you all.

[bitterly]
Mr. Bennet: The satisfaction of prevailing upon one of the most worthless young men in Britain might then have rested in its proper place. As it is, the thing is done - with extraordinarily little inconvenience to myself. When you take into account what I shall save on Lydia's board and pocket allowance, I am scarcely ten pounds a year worse off.

[Elizabeth gives him a Look that says she recognizes the irony of his self-congratulation. He looks down]

Mr. Bennet: I am heartily ashamed of myself, Lizzy. But don't despair; it'll pass, and no doubt more quickly than it should.