In Chapter 2: Preparations, O'Connell discusses a period of time when he repeated a word over and over to himself. What was the word and what was behind his behavior?

O'Connell notes that there was a time during his studies of the apocalypse that he began to mutter over and over again the word 'collapse'. He is still not completely positive why he formed this habit, but he reasons that it had something to do with his deeply ingrained fear that the world was doomed to experience complete destruction within our lifetime.