Don Quixote Chapter 18) Sancho says, “Come back, your Grace, Señor Don Quixote; I vow to God those are sheep that you are charging; Come back! O wretched father that bore me! What madness is this? Look you, there are no giants, nor knights, nor cats, nor shields either quartered or whole, nor vairs azure or bedeviled. What is this you are doing, O sinner that I am in God’s sight?”

Explain the section of the quote: "What is this you are doing, O sinner that I am in God’s sight?”