A mentor once told me that he wouldn't train someone that wasn't telling others of Christ on a regular basis. It seemed like a rather extreme statement at the time. I saw his point, but surely some just weren't ready yet. Or surely that could lead to legalism. Several years later, I see more clearly why he took his stance.
Heartfelt evangelism exterminates pride in a believer.
The best salesman in the world fails at redeeming the hardened heart. You can't wow them with theological knowledge. God must do something, and you have to pray. Evangelism, I began to see, was a relational issue. As I prayed to God to open the eyes of the blind, I drew near to God in fatalistic desperation at my inability to initiate rebirth.