The promise of suffering.
Of all the promises we have in scripture, John 16:33 is probably one of the least likely to be printed on a greeting card. Jesus was speaking with his disciples about rough times to come--persecution, suffering, hardship. He tells them that He is about to leave, but that the Holy Spirit would come to be with them. Then he said, “I have told you these things so that in me you may have peace. You will have suffering in this world. Be courageous! I have conquered the world.”
There are two promises in this verse. The first is that we will suffer. This certainly isn't comfortable and it isn't very encouraging. But this is not the only promise we have in this verse. The second promise completely changes how we face the first and it's this--Jesus has conquered the world and every hard thing in it. He is victorious. We can take courage and have joy knowing that He will and already has overcome.