Here is an example summary of this reading selection:

In “Bad Dog,” Maizes describes Chance, a dog who was aggressive with strange dogs (and people) but who provided the unconditional love Maizes needed to get through her divorce. Her relationship with Chance, and her other dog Tilly, taught the author about her own failings, and their unconditional love of her taught Maizes to be more loving and more forgiving.

Your summary will differ from this one in the way it is written, but it should include roughly the same information.