V.W.
unplanned purchases are usually the places where we bleed.
Try this:
ONLY spend cash. Get yourself an envelope and keep it in your purse with your cash in it. Everytime you take $ out of the envelope (even if it is $.50 for your kids' ice cream at school) put a receipt in the envelope right then. You can just write on a piece of paper 50¢ if you need to for those ice creams, or for a newspaper or whatever it is. HAVE to have a coffee or coke while you are out and about, and you spend coins?? ... write it down and put the "receipt" in your envelope.
At the end of the pay period or the month, you can pull out all the receipts and see exactly what you spent money on. Was it all necessary? Probably not. So you will know the next pay period/month what to NOT give in and spend on.
Also,
Fast food/drive-thru always ends up costing more than we think it will. So if you can avoid it, do. Make a sandwich at home and take it to work, or send it with your husband. Even buying a frozen dinner and heating it in the micro at work costs a lot less than a fast food meal.
Another thing to consider is that your budget isn't comprehensive enough. Did you list the $ you send to your kids' school for their lunches? Did you include the birthday card for your co-worker? (they can run $4.00 a piece these days). Did you figure in the money you are giving/donating in various places? (church, bell ringers, kids' school fundraisers, 'chipping in' for stuff at work). Did you include your annual expenses that you only pay once, or a few times at some point during the year? (homeowner's dues, school yearbooks, school pictures, Xmas gifts for people not in your family- like teachers, student gift exchanges, etc--, lawn care expenses (fertilizer, etc), newspaper delivery subscriptions, birthday gifts for your kids/spouse, gifts for birthday parties your kids are invited to, tax services, insurances (life/car/home owner's/renter's)...
When you sit down and REALLY write down all your anticipated expenses that occur throughout the course of a year it can be staggering. Did you include dentist visits? Eye glasses/contacts? Prescriptions you or a child need regularly or periodically?
Most people tend to remember all their "regular bills" like car payments, house payments, gas, groceries (food), telephone, cable/satellite, internet, etc. But forget that their grocery bill typically includes prescriptions, minor household or household repair items (tape, paper, school supplies, pens, duct tape, a new broom, a/c filters, cleaners, etc). And forget those "irregular" expenses like the myriad gifts required throughout the year, and doctor's appts and prescriptions, recurring subscriptions to magazines/newspapers, driver's license renewals, car tag renewals, and the like.
Write down. Write down. Write down. And write down again. You will have to sit down and review the budget (or just the list of expenses even) SEVERAL times before you really remember everything.
I happen to KNOW that I have an extra couple of hundred $ to spend in March, every year, b/c that is when my annual life insurance policy premium is paid. Initially, it always surprised me in the spring... and I went "oh no. I forgot that was coming due!" No more.