A helpful way to curb impulse spending and undisciplined financial priorities is to track every expense by category.
Using Quicken, MS Money, or a spreadsheet take 10 minutes a week to record all bills and receipts. Keep categories such as PropertyTax, AutoFuel, Tools, Entertainment, Insurance, EatingOut, etc.
This provides objective data to make a report over a period of months or years to identify irresponsible spending and to reprioritize purchase priorities.
A pattern of irresponsible spending cannot be changed by simply keeping records. There must be a heart-desire to honour Christ by stewardly use of the resources entrusted to you.