The whole world has a way through which it works - so mechanics don't change. Prabhupada says it's a change in the mentality. A devotee sees how everything can be engaged in the Lord's service. Just like when we cook for Krishna, we don't think of sense gratification but the cooking process involves the senses, like we see the food, smell the aroma but difference is the senses are engaged in the Lord's service.
The point is that the engagement is not different of any activity performed by a gross materialist. We may say that no, a gross materialist works differently. But how can we use God's creation, in a different way than God's Laws? If we have a machine, say a blender, does it mean that a gross materialist's blender will go one side and the pure devotee's blender will go the other side? Or when we drive a car, is it that a gross materialist's car goes frontward and pure devotee's car goes sideways. No, mechanics don't change but the
mentality changes. The activity/ work does not change but the quality or mentality of working changes.
We have this false illusion that mechanics change. Before joining Krsna consciousness, we are eating and sleeping and after joining Krsna consciousness we are eating and sleeping - but what changes is the quality of it and not the method. Cooking doesn't change, but how you cook, what you cook changes because of change in mentality. Earlier it was for one's own self and now it is for Krishna. The problem is we think we adjusted the impurity of the action, so it is 100% devotion. But if we don't use that action in the Lord's service or for pleasing Krishna, then it is still not pure devotional service.
- Excerpt from a Lecture by HH Bhakti Vidyapurna Swami :: Mayapur Jan, 2012