A common way to manage projects is management by exception. The rationale behind it is that we should only give attention to parts of the project that are not going according to plan. It makes sense. If parts of the project are going well, there is no use scrutinizing them.
However, if we’re only focussing on what’s deviating from the plan, we may be missing opportunities for improvement. If we use Pareto’s 80/20 principle, 80% of the work in the project is on 20% of the project value. This is no doubt the most expensive part of the project. Even if it’s going well, we may gain significant performance improvement by looking at the 20% most costly or most difficult part of the project, and looking for areas of improvement.