3. proud livery: gorgeous dress.

4. totter'd weed: tattered garment.

6. lusty: fresh and vigorous.

7. To say within thine own deep-sunken eyes: i.e., to say that "my beauty is buried in my eyes, which are sunken with age."

8. all-eating shame: shameful gluttony. thriftless praise: (1) unprofitable praise; (2) praise for thriftlessness.

9-10. How much more praise deserv'd thy beauty's use / If: i.e., the use to which you put your beauty would deserve a great deal more praise if. —"Use" can also mean "investment," which fits with the financial overtones of "thriftless" in the previous line and "sum my count" in line 11.

11. Shall sum my count, and make my old excuse: i.e., shall be the profit on my life's account and justify me forever.

12. Proving his beauty by succession thine: proving that his beauty is lawfully yours because he derived it from you.