To what extent do you "plagiarize" your own works?
Do you consider using the same or similar themes, passages and treatments across your own works should be considered plagiarization?
Or is it legitimate because it is taking from your own past works?
Are you aware of it when you engage in it? Or somebody else had better point it out to you because you are generally unaware of it?
And to what extent do you think composing in the very same style all the time and using the same formulas should also be considered a type of self-plagiarism?