Paul prayed three times that God would take away the "thorn in my flesh". Knowing Paul, those were no quick flash prayers - we're talking about serious praying. The answer was "no". Jesus prayed for his Father to take the "cup" of his sufferings away - he prayed so seriously that his sweat became drops of blood. The answer was "no".
Looking back at life, we can see many instances where our answer was "no", and with the advantage of hindsight we can see that "no" was actually the best answer. We got something else, or nothing at all, but that was the best that could have happened then. Imagine if Jesus' Gethsemane prayer was answered with a thundering "Yes!" from on high...
Yet, with all this past experience, every "no" hurts. No matter how often we confess that God knows best, no matter how firmly we believe that He's a good Father giving good gifts to His children, every "no" cuts to the bone. And you are not unique or sinful or backslidden to feel like that; the writer of Hebrews writes matter-of-factly that "no discipline seems pleasant at the time, but painful" (12:11) - it's human to hurt. But by the grace of God it is also human to eventually pick yourself up and accept the blessing of "no".
So, next time you have to swallow a "no", hang in there. Paul discovered that when God says "no" he does not leave you alone. The only person ever forsaken by God was His only Son, Jesus Christ...so that you will never ever be forsaken. The God of all comfort is right there with you. Cry on His shoulder.