Do not count your chickens before they are hatched.
So many times, especially these days we look to the future, counting on returns that we may never see. The state of the current economy should teach us this lesson all over again, though in all likelihood the majority of us will forget these lessons all too soon.
As we look to the future, it is generally good to keep a positive disposition. However a dose of reality can keep us from unhappiness. Spending money we have not earned, especially buying on credit is one of those dangers that we should heartily avoid wherever possible.