Being successful at budgeting requires you to know if the purchase you are about to make is a need or a want.
A need is typically an item that you have to have to survive (i.e.; food and housing)
A want is typically an item that you would like to have or something that makes your life easier or happier (i.e.; designer clothing)
Needs and wants are different for everyone and its important for you to realize which is which for you. Allowing wants into your budget is a good a healthy way to stick to the budget you created, just make sure you prioritize those wants within your income level.