John 16:33 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. 

There are things said ahead of time prophetically so that you will not be moved when you see them. Jesus tells us how to have peace in the midst of challenges, it is to be of good cheer because He has overcome the world. This is very instructive, but it is the greatest truth and reality. 

Here Jesus was talking about putting your faith in the finished work and build your faith and confidence on His victory. Be of good cheer, He has overcome the world. This truth is what leads us in the path of peace and victory always. If you focus on the world, the only thing you will see is defeat and discouragement. However, when you keep looking at Jesus, the author and the finisher of our faith, you will have peace beyond words. 

1 John 5:4 For whatsoever is born of God overcometh the world: and this is the victory that overcometh the world, even our faith.

Your victory is your faith in the Lord Jesus. Joy is one of our weapon of warfare for victory. No matter what is going on around you, keep an atmosphere of thanksgiving always. He has conquered the world, now rejoice and be glad.