The point is that it is easy to look back on different situations and remember them as better than they really were. It is also easy to lose sight of the fact that God remains in control and promises to use every circumstance in which we find ourselves for his glory and our benefit (Rom. 8:28). It is easy to let our circumstances drive us to complaining rather than worship.
When a new work is started, the newness brings with it a level of discomfort. We often refer to the old system as tried-and-true, even if the results were less than optimal. The danger is that the new work will be hobbled by those who are determined to force the new work into the old pattern. I have seen this tendency in industry and I’ve seen it in the church.