I do this. I have a daily planner with plenty of blank pages and write down, by hand, every transaction I make. I start with my monthly budget, subtract rent, groceries, a video game, a movie, etc. Anything beyond my budget, whether it's salary or a stimmy, goes to saving/investing.

It's been incredibly helpful for being aware of my spending. In fact it's so helpful I actually forgot how much I'm saving and was pleasantly surprised when I remembered how much it is. It's also very effective for staying on top of lifestyle creep.