The beautiful thing about books is that there are often so many editions of them, printed by different publishers in different years and in a variety of sizes and formats, such as paperback, hardback, and e-books. Because of this wonderful diversity, however, it is a virtual impossibility to assume that you and I share the same edition of the book and that therefore our page numbers will match. I shall do my best, however.

The copy of I Am Legend by Richard Matheson which I am using is the Electronic Edition published in 2011 by RosettaBooks LLC New York. The best I can probably offer you is the chapter and roughly where it is located after that. 

The first quote is spoken by the narrator, the "I" of the story, who is describing what his life is like now. We have all kinds of hints that something catastrophic and awful has happened; but, as he says, 

A man could get used to anything if he had to.

This quote is found in the first chapter of the novel, in the middle of the third page in my e-book edition.

The second quote is found about halfway through the chapter four, still in the the section entitled Part I: January 1976. Here Robert Neville is struggling to accept what has become his new reality. The full quote reads as follows:

After a while, though, even the deepest sorrow faltered, even the most penetrating despair lost its scalpel edge.

Neville does many things to dull his pain, fear, and loneliness, but here he admits that even the most horrible sorrows from another time have lost their impact now. Here he is again mourning the loss of his beloved wife, Virginia, at least as much as his emotions will allow him to mourn.