As you sent me into the world, I have sent them into the world. For them I sanctify myself, that they too may be truly sanctified. My prayer is not for them alone. I pray also for those who will believe in me through their message, that all of them may be one, Father, just as you are in me and I am in you. May they also be in us so that the world may believe that you have sent me.
-- John 17:18-21
When Jesus gets down to praying about and for the mission of the Church in John 17, he prays that we will be primarily about two things. And these two things are historically and currently the two things the Church tends to find the most difficult:
Unity with fellow believers
Evangelizing the lost