1. You have understated your expenses. Any actual expenses that were not considered in the budget will surely make you come up short.
2. You have not included “everything” in the budget. Some unforeseen expenses may include gifts, contributions and some small repairs.
3. You have failed to establish an emergency fund. The emergency fund will take care of the urgent items that were omitted in the budget. Furthermore, emergencies will not become an addendum to your monthly budget.
4. You failed to keep track of your spending. You have to update your list of what to buy when. Pay closer attention to trickier categories such as groceries.
You were not very stern to say “no” to yourself. The budget itself is in fact the very tool that would help you say “no” to certain things. Remember that saying “no” is tantamount to self respect.