You planned a budget in the beginning of the month and just after a week, you came to know that you are going out of it or unable to tackle it, try this way.
Example : If you are budgeted to spend Rs.100 each day, it turns to 3000 at the end of the month. On a particular day, a guest has come to your house and you had to spend Rs.120 which happens obviously with an additional member in the house. That is not in your hands, so then you should plan the next day in such a way that you might control any part of that extra Rs.20 you spent.
Analyze which part of the money you are spending on an item without which the day can be done, try to control your cost on that item on that particular day, next day too you can manage to do the same thing. Now you will get accustomed to this type of saving regularly and thus your budget of Rs.100 will reduce to 80 or much more lower.