Self-testing has helped me figure out that I my most challenging topic in Italian grammar is the application of the trapassato prossimo within the context of a text. While I am writing or speaking, knowing when to use it is generally quite easy. Or at least it seems to be. But when I do practice exams that require filling in the blanks of a text with the proper conjugation (person and tense) of the verb, I consistently fail. This can only mean one thing: I have a much worse understanding of the distinction between the verb tenses than I actually think that I do. I'm over estimating my ability and only become aware of this problem by consistently testing myself on all areas of the language and taking the time to think.
The retrospective period is a fundamental part of how I learn anything now. I've taken this from the Agile Software Framework that we use at work. Essentially I designate a period of time where I don't do as much studying. This gives me time to relax and let "diffuse mode" learning sink in while I do some self-testing and prepare my resources for my next intense round of learning.
Based on my evaluation of the mistakes I have been making I only have some minor problems distinguishing between when to use the passato prossimo and l'imperfetto so I really need to focus some attention up front on the trapassatto prossimo with some standard study and exercises. Then, I have some PDFs of various magazine articles that I have been slowly taking two or three paragraphs from and replacing conjugated verbs with their infinitive forms. I'll publish these at some point but as it stands right now, my time is quite contained with the exam specific prep period coming up in only a few months. I really need to fill in gaps in my learning before then.