budget blues

I've been using Quicken for quite a while to keep track of our monthly spending.
Ever since I took over the household accounting about two years ago, in fact.
It's a task I enjoy in a slightly hyperfocused kind of way.

I frequently tinker with the amount I set aside for various things, trying to constantly lower our monthly expenses and increase my rate of savings into various "pots"--tuition fees (9 more months!), Roth IRA retirement, 403 (b) retirement, and the wishful "home projects" (we now have plans for the attic addition, but not yet the funds).

Each month I "hide" or set aside money from various categories and release it as spent, so that when I look at what's left to spend what I see is the grocery money. I'm frustrated to see that we went $453 over budget this month, and at a loss how to explain it. I can see that we had some unusual expenses, including a building permit (the attic), home repair (paint and shelving), auto registration, and September school fees. However, each of those things was pre-budgeted for and I removed the money from the appropriate "pots" as needed (every month I set aside money for auto, pets, school fees, health insurance, etc etc, etc).

So where did I go wrong this month? I can see that we have way, way overspent on gas (sigh). We budget $55 and have already spent $112. We also had some health expenses (Minou's glasses and eye appointment), but again, I was reimbursed from a flex spending account, pre-tax, through work. I think that I probably didn't have enough pre-budgeted for some categories like school fees. We had some back-to-school shopping ($50) and some skin-care product shopping ($21), stamps ($10), movie rentals ($10). But those items don't add up to $453. What happened?!

I'm seeking some balance. I want to know how much we have and stick to a budget. I want to save, save, save to meet our many goals. But if the budget isn't realistic, it also won't work.