When Jan-Lukas mentioned considering and then implemented a private mode on his site to act as a journal I was instantly reminded of my own decisions in that regard.
It was almost three years ago that I first made the WordPress plugin that creates a private custom post type but, as that was all it was, it just didn't stick. I went analogue for a while writing both morning pages and daily gratitude logs as a way of journalling but, again, this didn't happen entirely naturally and eventually stopped.
As Jan-Lukas says, the ease of journalling is what's important — reduce the friction and you're more likely to keep going. Once I had the custom layer built on top of WordPress the rest just fell in to place. The custom post type is still exactly the same but the way I post and update journal entries is now so effortless that I've been able to keep it going — A 75 day streak now and counting. Having an almost identical process for the blog, journal and garden has really made the difference.
I've not replicated the old analogue routine entirely although I do tend to write something at the start and end of the day. There is, however, the added flexibility of being able to take out my phone and, at any time, add a quick note — not always possible if you're using pen & paper. Yes, writing on paper makes the brain work in a different way but I'd rather have the consistency of getting something down every day than not write at all.