Previously Sprint Retrospective is discussed in Scrum Activities.
Here the idea of a retrospective on the fly is underlined. It means the project team should be open to the form or common rules of the retrospective meeting but start the retrospective meeting whenever necessary.
Be sure to conclude the pros and cons of a sprint before the end of the sprint. Be agile, be responsive to essential findings on the fly, and be flexible.
This idea is easy to understand but is not the least important. Like dependency resolving, a retrospective on the fly usually aims to address real-time issues in production. It could minimise the impact of cons or uncertainties on the project and help it secure progress and success.
Typically retrospectives are scheduled periodically, but you should adopt the mindset not to restrict the timing.
Whenever you realise issues are about to come into being or problems are already there. The issues with significant impact must be resolved before the regular retrospective meetings; it is urgent to set up a retrospective at once.
Do's
Don't
Main elements in the example