Comrade, you have an incredible calling on your heart to bridge people from different cultures together in Christ. While listening and reading through the PP provided this week, I too was encouraged by the reminder that the church/we/I do not own the missio dei, but that we are invited to participate.
In regards to concerns of maintaining a consistent level of enthusiasm in the hearts of short term missionaries, the imagery of the meme on slide 15 of the Global perspective PP really spoke to me. In this imagery I saw a symbol of the Father carrying us (all missionaries) into mission and never letting go as long as we hold on to His love. The message I received was that we cannot control how the Father holds us or where He carries us. We must trust what He is doing in one an others heart and that Spiritual growth is something only God knows.
As Spiritual growth in all of our lives goes, it’s always easier to say or lay out a plan for ourselves, than to actually bear fruit. I too struggle from observing what I see sometimes in missionary settings, but am hopefully soon reminded our Father has us along His shoulders for our own unique role for His all inclusive purpose.