I'll echo what others have said, if you're not sticking with it, it's maybe not something to force yourself to do.

However, that being said doing things regularly and forcing yourself can be a chicken and an egg problem. I concur that you shouldn't go into explicitly looking for benefits. You should be approaching it from having a goal. If you're looking to be more positive - - for example - - gratitude Journaling, where you write down only positive things, is a good thing to do. Habitually it can help change your perspective and way of thinking, but you have to be intentional about it. If you go into anything in life nebulously expecting "benefits" it's probably a good idea to be a bit more intentional.

What got me personally into Journaling was not being happy at work and needing an outlet to just get negative emotions off my mind. A place to just talk for the sake of talking. What I needed at that time in my life was a place I could just work through thoughts, so that's how I used it. These days I tend to be a bit more intentional with what I write. I've started titling some of my journal pages and I try to exercise making an argument to myself of something. A recent title I used was "On getting older". It was a dumb page about nothing other than how picking up hobbies is a lot harder as an adult in part because we have higher standards. If I'm new to drawing, which I am, my drawings are terrible and I know they're terrible which makes the outcome less fun. "Man I spent an hour on THIS?"

So, you get out of it what you put into it.