Having been in exactly this position (not in a debt hole, built a budget to get a better view of what spending is), I can say what the greatest gift it brings is: it's a decision tool.
When you are spending out of only one account, you often make decisions based on the total money in the account. “Should we go out for dinner? Can I make this impulse purchase?” This is terrible, because many, if not all, of those dollars are already intended for certain future expenses like groceries, bills, etc. You can't see how many of those dollars are discretionary.
A budget is like having many accounts. Instead of looking at your real account(s) to make spending decisions, you look at your budget lines. You to want impulse buy a gadget — do you have money remaining in a relevant budget line? If yes, the decision is yours, if no, the budget is telling you that you don't have dollars for that.* Similarly for more prosaic purchases — you want to splurge on some non-staple groceries to make a fancy dinner or try out a new recipe, and the budget line for Groceries will tell you if you can do that. Instead of looking at (e.g.) $6000 in a chequing account, you're looking at $600 (assigned) − $146.86 (spend) = $453.14 (available) in a monthly groceries budget line.
Just like you can now see where your money has been going, by maintaining and using your budget lines, and having every single dollar you spend go through the budget (to show your totally assigned, total spent, and total remaining), you can continue to see where your money is going in near real-time. You're no longer looking at bills and statements to figure out what's going on and plan, you're looking at money flows and future intentions, as you should be.
This approach to budgeting has completely changed our finances.
- Instead of feeling like a weight, we actually enjoy paying off our bills — it makes the budget tidy.
- We feel free and guiltless to spend money that has been earmarked to spend freely. (Having a personal “fun money” line is how we do it. I've heard of others with multiple budget lines devoted to the same overall personal spending amount, in order to sub-budget that money. Whatever works for you.)
- We are appropriately miserly when considering other budget lines. Do we want to change our (e.g.) cable package? This new feature is only an extra $4.99 a month (“that's nothing!” we would have thought before)… but is it really worth it to increase that bill's budget line by $4.99 a month, because we have to ask ourselves from which other line do we subtract it?
- Borrowing money in a smart way is easier, since we can see exactly how it affects current available funds and compare that with projections of how it affects future available funds. We can plan precisely for how to pay it off, and see how it affects the budget of future months. No longer do we have “borrower's regret”, where the reality of future payments is more painful than anticipated.
So that's what a budget is for: real-time spending decision-making control over your money, which for us has translated into a lovely mix of painless austerity in spending categories where austerity is smart, and guilt-free spending in more indulgent categories because we have already determined exactly how much we can afford and wish to spend.
* A budget line with insufficient funds doesn't actually take the decision entirely away from you though. If a budget line doesn't have funds to spare for a given purchase, you can still make the purchase — but now you're also making the decision to go and revise your budget, taking dollars away from other budget lines to adjust the line you've overspent, to keep the budget accurate.