I found in an English learners’ textbook a sentence which goes, “Many people helped me on my journey.” That’s no problem. That makes sense to me. What about “in my journey?” Both seem to be okay. However, Google Ngram Viewer says “in my journey” is used a lot more often (https://books.google.com/ngrams/graph?content=in+my+journey%2C+on+my+journeys+&year_start=1800&year_end=2000&corpus=15&smoothing=3&share=&direct_url=t1%3B%2Cin%20my%20journey%3B%2Cc0%3B.t1%3B%2Con%20my%20journeys%3B%2Cc0). Then comes up a question. This extract is from a English textbook for Japanese high school students at a lower intermediate or beginner level. Then why “on my journey” rather than “in my journey?” I wonder if “on” is preferred in this context?

I found in an English learners’ textbook a sentence which goes, “Many people helped me on my journey.” That’s no problem. That makes sense to me. What about “in my journey?” Both seem to be okay. However, Google Ngram Viewer says “in my journey” is used a lot more often (link). Then comes up a question. This extract is from a English textbook for Japanese high school students at a lower intermediate or beginner level. Then why “on my journey” rather than “in my journey?” I wonder if “on” is preferred in this context?