I used to overspend, not to the point where I had no money left but after budgeting more carefully I actually wondered what I had been buying. My motivation was a mortgage deposit and I made an Excel spreadsheet with all direct debits, incidental expenditure and incoming payments, a big balance sheet.

I haven't updated it for a month (tut tut) but it can tell me to the penny what should be in the bank and what I'll have in the future on my current spending and income rate.

Now I just use the cash machine once a week, any leftover cash I put aside to dip into if anything comes up.

Like Hustler25 said, don't buy frivolous items. I haven't ate fast food for years and I used to be a bit of a gadget fiend but get by on what I have.