Yes. Self-observation, especially self-observation of pain and other bad and should-be-improved points, and the method of improvement deriving from the self-observation.
Does the chapter 2 in Tusculanae disputationes go into that matter ?
As to Thomas Aquinas' Quaestiones Disputatae De Anima,
as I looked into the article 21, the view that the pain is peculiar to the body, and even in mental sufferings what is really suffering is the body, doesn't seem to be of Thomas, but of someone other.
But what I read before was not Quaestiones Disputatae De Anima. It was probably The Commentary to Aristotle's De Anima by Thomas Aquinas, or De Malo by him.
I have to search into those books to find the passage.
Then, could you advise me how to search as easily as possible.
(I have never been taught the method by a teacher.)
Do I just search the books bit by bit, taking several days or weeks ?
Recently, I got a vision on what I should research and study from now on.
It's about searching for the texts on self-observation.
And for now, if there really was that view I mentioned above, I want to trace it historically.