What is hope? According to Dictionary.com hope is "To wish for something with expectation of its fulfillment."
But why should we be hopeful, even when we get let down, when things don't turn out right?
If you don't hope and believe that things can change, or get better, then they will not. Good stuff rarely happens to people who believe it can't happen to them. If I believe America will continue down the path of governing by political parties that don't serve the people, then I will act in a way that will not promote the change, thus making it more unlikely. By hoping that change can actually occur, it will become more likely.
Likewise with personal goals, if I don't believe I can do well in math, sure enough, I won't. But if I hope that I can do better, and act in a way to achieve those ends, it is very likely.
Hope things can get better, and hold on to your dreams, if they will truly make you happy.