Author and protagonist Paul Kalanithi states that as his health declined, he found himself repeating a quotation from the Irish author Samuel Beckett. These lines, which he had learned while an undergraduate student, are “I can't go on. I'll go on.” The lines form part of a long passage in Beckett’s novel The Unnamable.

In When Breath Becomes Air, Kalanithi speaks candidly about the difficulty of thinking about the future while he was a terminal cancer patient. He explains that for a period of time, he could only think about the future in terms of doubt; it presented a “monolithic uncertainty.” He did not consider that he had any options. Rather, he saw “the shadow of death” as blocking his ability to derive meaning from any action. Kalanithi credits literature in general as well as Beckett’s specific words with bringing him back to life. At one particular moment, he experienced an epiphany. Waking up in pain yet again, and not being able to think of anything that would happen later than breakfast, Beckett’s words occurred to him. From that time on, whenever he thought “I can’t go on,” he always followed it with “I’ll go on.”

In Beckett's novel, the unnamed main character struggles to continue with daily life. In a long passage in which the character reflects on existence, pain, words, and storytelling. At several points, they seem to hear another person saying, “You can’t go on,” followed by “I can’t go on.” The character states their belief that “You must say words, as long as there are any,” because silence would indicate the end of being. Finally, the character affirms, “I’ll go on.”