None really. I think I’ve always been in a privileged enough position that I never really needed to worry. I’m not a big impulse buyer and tend to regulate myself on this. If I buy something that I don’t really use as much as I thought I would, it annoys me so much that I become much more conservative with spending in the following weeks/months. It kinda self-regulates.
I don’t have a car, and instead bike everywhere or use public transport which saves me a lot of money. This is again a privilege, because I managed to land an affordable place to live that’s close to work.
My only way of keeping track of all this is the division between my payment and savings accounts. If my payment account goes above a certain value, I move money to my savings account. As long as this keeps happening regularly, like it has for years, I have nothing to worry about. Obviously I do check the details of my spending every now and then, but nothing organised.