If you read the Bible for long, you'll come across a well-traveled passage in Romans:
Do not be conformed any longer to the pattern of this world, but be transformed by the renewing of your mind... (Romans 12:2)
I like this passage because it says that our lives will never be completely transformed until we allow God's Spirit to renew what we think about. Renewal - to make new again, to make fresh - helps us take in the world differently and therefore we can respond to the world differently.
The problem is that I think about garbage many times. I think about my golf swing. I think about my virtual golf swing. I think about sports. I think about sex. In and of themselves these aren't wrong per se, but the exaggerated and prolonged meditation on these things can be destructive because those thoughts will set my motivations for the day. So, exaggerated thinking about my golf game will determine how I carry out my mission for God that day. Frightening.
Into this discussion enters this question from Dallas Willard:
Does our mind spontaneously return to God when not intensely occupied, as the needle of the compass turns to the North Pole when removed from nearer magnetic sources. Our answer to (this) question makes us sadly aware of how our mind is solidly trained in false ways. (Hearing God, 153 paraphrased)
What do we think of when we have nothing to think of at all?
Where does our brain go when it has no where else to go?
What happens if we trained ourselves to, as Frank Laubach suggested, think on God one minute of every hour of every day and build up from there?
How would our mission to the world in our communities and workplaces change if we became incurably mindful of God-at-work in our midst?
The key to formissional living is to have our lives formed around constant thinking on the missional God working in the here and now.