I've been meaning to start a thread about the budgeting app You Need a Budget (YNAB) as I know a number of us use it. I regularly recommend it on MN but just to stress I have absolutely no affiliation with the company, it's just what works for me to keep my budget (mostly) on the straight and narrow.
YNAB currently have a 33% off sale, so it's selling for £27.99 in the Mac App Store, just slightly less if bought directly from their website, depending on the exchange rate you get.
The site is worth a look even if you don't want to buy the software - the method could be done just with spreadsheets if you wanted to (in fact it started life as a spreadsheet app) and all the training material is freely available, including the live classes.
The key thing for me has been learning not just to juggle monthly expenses but also plan for the less regular or less frequent ones. These tend to be the ones that wreck a basic budget, however carefully the monthly expenses are accounted for. The ability to move money between the various pots as required means you can make decisions mid-month, i.e. [x] becomes available on sale, you want to grab it, so you have to decide what of [y] you'll do without to make the budget balance.
Anyway, I'm hoping at least to tempt Oberon out of hiding to find out how he's getting on with YNAB after our budgeting software thread last year.