Role of Worship in Missions

From Piper's "Let the nations be glad!: the supremacy of God in missions":

But worship is also the fuel of missions. Passion for God in worship precedes the offer of God in preaching. You can't commend what you don't cherish. Missionaries will never call out, 'Let the nations be glad!", who cannot say from the heart, "I rejoice in the Lord....I will be glad and exult in thee, I will sing praise to thy name, O Most High" (Psalm 104:34; 9:2). Missions begins and ends in worship.

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Even outsiders feel the disparity between the boldness of our claim upon the nations and the blandness of our engagement with God.

Though I'm not sure non-believers would be able to see the disparity between a passion for missions vs. a passion in a believer's own walk, they would probably be able to detect hypocrisy and disparity between one's beliefs and actions in at least local contexts.

It is possible to be distracted from God in trying to serve God. Martha-like, we neglect the one thing needful [...]

Yes, our attempts in and of themselves are just that...attempts. There needs to be some fuel to spark the fire.