I find in the writings of our Hecato that the limiting of desires helps also to cure fears: "Cease to hope," he says, "and you will cease to fear." "But how," you will reply, "can things so different go side by side?" In this way, my dear Lucilius: though they do seem at variance, yet they are really united. Just as the same chain fastens the prisoner and the soldier who guards him, so hope and fear, dissimilar as they are, keep step together; fear follows hope. I am not surprised that they proceed in this way; each alike belongs to a mind that is in suspense, a mind that is fretted by looking forward to the future. But the chief cause of both these ills is that we do not adapt ourselves to the present, but send our thoughts a long way ahead. And so foresight, the noblest blessing of the human race, becomes perverted.

--Seneca, Moral letters to Lucilius, letter 5

All disappointment is a result of our expectations (hope). One should do what they can when they can, and not let hope and fear overcome their reason.

So there is no hope?

Hope was the last thing to leave Pandora's Box. John Cleese, in Clock Wise, says "It's not the disappointment. I could tolerate that. It's the bloody hope!"

You may have confused hope with gullibility.