Mostly, I journal at home on my dining table. But, while I was on a trip recently, I felt the need to journal and of course didn't have my trusty typewriter with me. Writing on my phone would have been easy, but I felt that, in doing it that way, I would have missed the physicality of doing it on paper.
So I gladly accepted it as an excuse to go to the stationery store and browse the journal options. Given that I tend to like medium- or broad-nib pens -- in fact, I've recently fallen in love with a stub nib fountain pen -- I knew it'd have to be bigger than the pocket-sized options. For my Goldilocks combination of carrying size, size during use on a train or flight, fountain pen compatible paper, and minimalism, I ended up with a Mnemosyne 104. I've done one entry in it, but I plan to tear out the page and enter it into my springback binder, with all the looseleaf I usually use with my typewriter, so that it is integrated into my chronological order.
I realized that I didn't really care if people on public transit next to me were reading what I was writing.