An unfortunately common practice goes like this (warning: don't try this at home): Suppose you are out of money in your checking account; however, your local grocery store will, as a convenience to you as a customer, cash a check for you. So, you cash a check for $\$ 200$. Of course, this check will bounce unless you do something. To prevent this, you go to the grocery the next day and cash another check for $\$ 200$. You take this $\$ 200$ and deposit it. You repeat this process every day, and, in doing so, you make sure that no checks bounce. Eventually, manna from heaven arrives (perhaps in the form of money from home), and you are able to cover your outstanding checks.