Hebrews 10:1-18 concludes what the author has been saying in the first 9 chapters.
He does this by contrasting the shadow with the reality, and then the author reminds us of the temporary nature of the old covenant sacrifices along with the once and for all completed work of Jesus on the cross.
The letter to the Hebrews was written to encourage Jewish believers that their faith in Christ was not misplaced. That Jesus was in fact the reality of which all the old covenant ceremonies and sacrifices were but shadows. Although this letter was written to Jewish Christians, we can all profit from the warnings, encouragements and instructions of this great letter.