Unity is a crucial element to testify to the world that Christ is the Son of God. May they also be in us so that the world may believe that You have sent me. This takes effort. Pray fervently for their spritual struggles, mourn over their setbacks, stand with them in the battle, lending any aid that you can. To be frightened is to demonstrate a lack of faith in the cause of the battle, the strength of the army, and the wisdom of the general.
Fear betrays a lack of faith.
On the other hand, faith casts out fear. We in Christ, in the strength of Christ, and under His guidance, have nothing to fear from our enemies. Our courage in the midst of opposition is a great testimony to the world that our faith is true. Our courage is proof of their condemnation, proof that they are allied against the True and Living God. Our courage is a sign to the enemies of God that our salvation is truly from God, and not a cleverly devised fable.