Here's why:
* Reflexive pronouns refer back to the subject of the sentence. They are used when the subject of the verb is also the object of the verb.
Examples:
* She hurt herself. (The subject "she" is also the object of the verb "hurt".)
* They congratulated themselves. (The subject "they" is also the object of the verb "congratulated".)
In both examples, the reflexive pronouns "herself" and "themselves" refer back to the subjects of the sentences.
Let me know if you have any other grammar questions!