Which sentence in this excerpt from Leo Tolstoy's The Death of Ivan Ilyich shows the human tendency to contemplate one's past life?

Depends on which excerpt and sentence that you are referring. Leo Tolstoy's The Death of Ivan Ilyich was first published in the year 1886. It is a fiction story that focuses on the religious conversion of Leo Tolstoy during the late 1870s. It is considered as one of the masterpieces of Leo Tolstoy.