Set yourself a budget -

and stick to it. Food, bills, rent going out. it all starts to add up and if you don't budget, things can go wrong very easily. If you tend to spend money as soon as you get it, try setting yourself budgets over smaller periods of time rather than a term - say on a weekly basis. Take out the money you need for that week and discipline yourself not to go near an ATM until the same time the following week.