""These things I have spoken unto you, that in Me ye might have peace. In the world ye shall have tribulation: but be of good cheer; I have overcome the world." John 16:33
When Jesus says, "These things I have spoken unto you, that in Me ye might have peace" Jesus had just explained to His disciples about His death, resurrection, the condition of the world, and some expectations concerning suffering while in the world. Let me get this straight. You tell me about your death and how difficult things are going to be for the believer as they manage being in the world but not of the world and I should be at peace? Yes. Jesus has expectations too, expectations that you and I are listening and comprehending what He is saying.
Keep in mind, this is not after His resurrection. Jesus overcame the world before He was crucified. Because He overcame the world while He was crucified, so can you. You really need to get the part about Jesus speaking. "These things I have spoken unto you." What Jesus speaks comes to pass. IF Jesus has spoken unto you, what Jesus spoke unto you will come to pass. Every word that Jesus spoke that is recorded for us has come to pass or will come to pass in its time. The time you now live in is a time Jesus spoke of and Jesus says to be of good cheer. Jesus says He has overcome the world. We are joint heirs with Christ and every available tool of God has been and is being used to take us through the world as overcomers and in good cheer.
Its possible that in your current situation you just don't feel like having good cheer. There are many things that fit that premise. Part of why we have so much disappointment is because we have such a myopic view of life. If we were to truly look at the events of the day and the situations of life through the eyes of Jesus, we would have a God size view of God. With a God size view of life, it all works and there is reason to have good cheer.