Jack Kerouac was a prolific writer. He left us over 30 books (prose and poetry), hundreds of letters, many journals, and whatever lurks in the estate archives that is yet to see the public light of day. Given that, it is no wonder that similar phrases appear more than once. I don't see this as a problem whatsoever, just something to note. You can't plagiarize yourself (well, technically it is possible from an academic standpoint). I prefer to think of it as "recycling." In other words, Jack was green before it was cool. Indeed, the Day 71 Kerouaction in my book -- The Beat Handbook: 100 Days of Kerouactions -- is on that very topic. Click here for that entry.
This is neither the time nor place for an exhaustive list of recycled Kerouacian phrases, but I will provide one example that struck me for the first time in my recent effort to get you to read The Dharma Bums along with me (check the archives on the right for all 34 chapters summarized in one sentence).
If you ever receive an e-mail from me, you will see that my signature includes this line from the very end of Big Sur (p. 216 in my 1992 Penguin Books edition):
Something good will come out of all things yet.
I love the optimism of this line. As I was re-reading The Dharma Bums in order to complete my recent one-sentence chapter summary project started on December 19, 2018, I happened on this sentence near the very end of Chapter 29 (p. 210 in my 1976 Penguin Books edition):
I know something good's gonna come out of all this!
I thought: "That's from Big Sur!" Not exactly, of course, but the similarities are axiomatic. For context, The Dharma Bums excerpt is spoken by Japhy Ryder. The Big Sur excerpt is the narrator, Jack Duluoz, speaking. Written in 1957 and 1961 respectively, it is easy to see which work borrowed from the other.
What recycling have you noticed in Jack's works?