The main theme is the bitterness of the human heart. When a person dies it marks their extinction from the physical world, but also from the hearts of their loved ones. This is shown in how the persona continues to make guesses of who is digging up her grave (her husband, kids...), however each of these are wrong. Also, this is shown through how her husband has already remarried, and her kids are doing other things. Furthermore, this extinction of her existence from their hearts is furthered by the contrast with how a dog's loyalty is far greater than that of humans.