I remember a Youth Minister saying years ago "My problem is not motivating people; My problem is people DE-motivating me!" From years in ministry I have learned the hard way that People will disappoint you. People will oppose you. People will see themselves in competition with you. Sometimes in your own family. (even in your church family!) And I must admit that it can be a real downer to see your fiercest opposition coming from other Christians.
But Paul was able to see beyond the petty attitudes of these competitive Christians. He said, "But what does it matter? The important thing is that in every way, whether from false motives or true, Christ is preached. And because of this I rejoice." Philippians 1:18