For example if you know that you need to spend 20 dollars a day on average for food and transport, put only that amount in wallet!
You can spend as much as you like in that wallet knowing that you will NEVER bust your budget. Avoid using Credit Card. (unless of course its an emergency)
Whatever that is left over for the day, put it in a box or something at home. At the end of the month, give yourself a treat using what's left!