credit/debit cards are linked to your banking account. So the money you spend is automatically deducted from you account.
Debit cards can also help your budget.Use your card to pay your bills and day-to-day expenses and your and your monthly statement will provide a good snapshot of how much you spend per month and where it's going.
Unlike credit cards your bank balance goes down with each debit cards transaction ,so you're less likely to over spend .(many banks offer over draft protection "that allows you to exceed you balence.