In this post-crash economic age, financial irresponsibility is intensely frowned upon. Buying on credit, spending cash you don't have and making unnecessary purchases are all features of an unhealthy relationship with money, and, if you are keen to make the most of your funds, you will need to sort these out.
To begin with, it is very important that you take stock of how much money you have coming into your accounts, and how much you spend every month. Before you have a well-charted budget, you simply can't know if you can afford that new cedar roofing or not.
The first step in defining your budget is simply to calculate your income. Work out how much money you make and write that figure down at the top of a clean page. From it, subtract all of your big debit order expenses: your car payments, your rent and your insurance, for example.
You will now have a smaller figure to work with: write this down and then minus your living costs - groceries, domestic utilities and the like. This might take some working out, but with a little effort it shouldn't be too difficult to work out how much you spend on food every week.
Continue in this vein until you have dealt with all of your expenses. If, by the time you reach this point you don't have any money left or, worse, you are in a negative balance, it is definitely time to reconsider your finances.