Any true healing begins with deep repentance, and the first duty of repentance is contrite prayer. If you haven't recently confessed your lack of evangelistic zeal, then the following prayer might be a good place to start. Pray it carefully, and as you pray, ask the Holy Spirit to help you mean what you are praying.
"Father and God, we confess that we have accommodated ourselves to the idea of most people not knowing You. We confess that we have believed what nonbelievers say about themselves, which is that they have a right to remain in their unbelief.
Father, we confess that we live in a nation that believes that it has the right to not come to You, and we confess this sin on their behalf.
We know, Father, that if we in the Church regard iniquity in our own midst, or in our own hearts, this prayer will be ineffectual. Father, we confess that we in the Church have been lethargic in our evangelism. We ask that You would forgive us for this, and that You would stir us up with a zeal for others to come to know You.
And Father, we also confess our own sins to You now—Selah . . . We do this in the majestic name of Jesus our Savior, and amen."
(Pastor Douglas Wilson, Christ Church, Moscow, ID)