These things I have spoken to you,
that in Me you may have peace.
In the world you will have tribulation;
but be of good cheer, I have overcome the world.
Just prior to these verses, Jesus has told his disciples that His hour has come; they will all scatter and leave him alone. Yet He won't be alone, because, He tells them, "My Father is with me." So when He says, "These things I have spoken to you, that in Me you may have peace", He is telling them (and us) not to be distressed about the hour that is coming upon us. We may feel the heavy burden of approaching trouble and suffering, but we are to rest in the knowledge that our Father will be with us, just as He was with His Son.
Ever since Adam and Eve disobeyed God in the Garden, this world has been an endless fabrication of trials and tribulations. Indeed, He tells us flat out that "In the world you will have tribulation".... not that we "might" have tribulations; or "it's a possibility" that tribulations will happen in your life; but that you WILL have tribulations.
But we are not to immerse ourselves in these troubles. As the photo above illustrates, Jesus is our Good Shepherd. We hear His voice and it brings peace into our troubled minds and hearts. If we will follow that voice, we can know joy in the midst of our troubles. And if we can concentrate on that joy (peace), we can actually live outside of the circumstances that are so worrisome and tormenting. Think of it as a parallel universe, if you will.
It doesn't mean that we can escape the troubles. It doesn't even mean that we will not suffer through them. But it does mean that we can begin to see things from Jesus's perspective. We can begin to gain a true understanding of the relative importance of things. We should try to overcome the weight of our earthly troubles and concentrate on the significance of our eternal promises.
Jesus is our example. He was faced with the worst persecution known to mankind, yet He looked forward to overcoming what the world brought against Him. That is the peace He offers us. That is the joy we can experience, knowing that He identifies with us and we can share in His victory. We cannot be defeated!