| Quote #1
"He suffered terribly the last few days."
We're told right off the bat to expect Ivan's death to be a very painful one. We're also given an insight into just how selfish Praskovya Fedorovna is. Look how quickly she moves from Ivan's suffering to her suffering. She's obviously appealing to Peter's pity. Not only that, it's not even clear that Praskovya suffered because it hurt her to see her husband suffer. It almost sounds more like she just found the loud noise he made to be disturbing.
| Quote #2
"Three days of frightful suffering and the death! Why, that might suddenly, at any time, happen to me," he thought, and for a moment felt terrified. But – he did not himself know how – the customary reflection at once occurred to him that this had happened to Ivan Ilych and not to him, and that it should not and could not happen to him, and that to think that it could would be yielding to depression which he ought not to do, as Schwartz's expression plainly showed. After which reflection Peter Ivanovich felt reassured, and began to ask with interest about the details of Ivan Ilych's death, as though death was an accident natural to Ivan Ilych but certainly not to himself. (1.44)
Peter Ivanovich is initially scared to learn of Ivan's suffering because it occurs to him that he could undergo something just as horrible. But it's not long before he has the same reaction to suffering he has to Ivan's death: he just denies that it could happen to him. And once he makes that move, every detail he learns about Ivan's suffering only makes him less sympathetic. The worse it sounds, the less believable it becomes.
| Quote #3
But this discomfort increased and, though not exactly painful, grew into a sense of pressure in his side accompanied by ill humour. And his irritability became worse and worse and began to mar the agreeable, easy, and correct life that had established itself in the Golovin family. Quarrels between husband and wife became more and more frequent, and soon the ease and amenity disappeared and even the decorum was barely maintained. (4.1-2)
All it takes is a little discomfort for Ivan's life to start falling apart. Because Ivan just lives for the sake of enjoying himself and keeping everything pleasant, the moment things become unpleasant he can no longer handle the situation. His characteristic good mood goes pretty quickly, and his family relations go bad almost immediately.