My first tour was quite unintentional. After years of a bad marriage, my (then) wife had me leave—but she wouldn't give me one of the (three) cars. I expect that she thought that that would "keep me around," but it didn't work like that. I had had enough and was going back home to the shore.
A daypack and a gym bag with a few shirts, underwear, etc. I'd been laid off of work the week before. A mountain bike with a racing seat and 150 miles to go. My butt killed me. Took me two days, but it was the most fortuitous ride I ever took. Then I found out about panniers and "real" bike touring and the die was cast. I had been bike packing before, but had no idea about road touring. I found out.