Introspection is the mental process shown mainly in autobiographies in which the writer analyzes and formulates a judgment of his or her mental state. It is a self-declaration of one’s own mental or cognitive either decline or progress.
In this excerpt from the Autobiography of Benjamin Franklin the two sentences that show the narrator's introspection are:
“In truth, I found myself incorrigible with respect to Order; and now I am grown old, and my memory bad, I feel very sensibly the want of it.”
“But, on the whole, tho' I never arrived at the perfection I had been so ambitious of obtaining, but fell far short of it, yet I was, by the endeavour, a better and a happier man than I otherwise should have been if I had not attempted it; as those who aim at perfect writing by imitating the engraved copies, tho' they never reach the wish'd-for excellence of those copies, their hand is mended by the endeavor, and is tolerable while it continues fair and legible.”
The first two sentences from the first paragraph are the ones that show introspection best.