With a mobile app I do track all my expenses and gained money. I dont make it very detailed, like putting down list of every food and product I buy, but I have record of major categories (food, fun, services, purchases, education, vacation, vehicle and etc). Not only it helps to balance expenses, as I see where I have already spend a lot this month, but it works as a reminder of past prices. For example I cant always check in no time how much I have paid for service (helps a lot when its car fixing time).
I have starting keeping spending record when I have met my future wife. I have started spending crazy (to make an impression), and spending record helped me to realize that I should slow down on expenses, otherwise I would go broke really fast.