When the preacher or teacher talks about money, the room gets quiet. We have the sense that we are not doing very well at it, and we are ashamed because we know evangelism is so important and so urgent. We should do it out of love for God, we say, or as obedience to His command, or as a response to His love. But this much only scratches the surface.
Evangelism is a matter of boasting.
Think of the obstacles that seem to lie across our paths. We don't to say anything that might upset our friends. We don't want them to think less of us, for we don't want them perhaps to cease being our friends. Or don't want to embarrass ourselves. Deep down we sort of like ourselves this way.