Question pertaining to Great Expectations.

In chapter 37, I do not understand the deal Wemmick and Pip are making, and the deal with Clarriker's house. The passage- "At length, the thing being done, and he having that day entered Clarriker's house, and he having talked to me for a whole evening in a flush of pleasure and success, I did really cry in good earnest when I went to bed, to think that my great expectations had done some good to somebody." It seems as if the chapter was significant, and I guess my mind did some wondering while reading it. Anyone care to explain what's going on?