Hope deferred

"Hope deferred makes the heart sick, but a longing fulfilled is a tree of life" -Pr 13:12

Right now I am really struggling with this scripture. I just don't understand how to protect your heart from the pain of an unfulfilled hope. Should we not dare to hope for anything unless we are 100% sure it is God's will? There are longings and hopes I hold deep in my heart, and they are only making me sick . . . but I can't seem to let go of them. And it doesn't seem right to just because they don't seem probable. The Word also tells us to pray with faith, that if we really believe God will grant our requests. What is the answer? To hope or not to hope?