"O, woe is me!" This line is from Shakespeare. When Hamlet scorns Ophelia, she utters these words to express the grief and despair that will soon drive her to suicide.
Another famously dejected figure, Job, echoes this unhappy cry in the Old Testament when he contemplates his sad fate, "If I be wicked, woe unto me." Today, woe generally means problem or worry. You may experience financial woes, if you spend too much on your credit card. And study hard for your classes or in addition to your academic woes, you may get grounded by your parents. Sometimes woe is used in a slightly ironic way. If your friends tell you to forget about your woes and go out with them, they think your problems are not too serious.