There are 2 posts related to #natural-planning-model tag.
From Reactive Planning Model to Natural Planning Model
Until some point, the project was manageable, but after some feature requests and bug reports, it became unfeasible. In addition, almost every bug fix or feature implementation broke other "uncorrelated" parts of the application. That slowed us down a lot because our client and his customers were using the software, and we had to rush to fix the new bugs (yes, we didn't have testing at that time).