When practicing any of the agile software development methodologies – despite an inherent flexibility of those – it is rather important at least to start with a “by the book” approach. This means that when you roll out your agile processes, you try to implement each and every aspect of it, even if that seems useless or not required in your particular situation. Only then you can see from experience that something needs to be tailored – and a retrospective is a powerful tool to facilitate that kind of team learning.