She's talking about in the beginning how she was upset about it, how she couldn't sleep because she thought about it. But by the end of the song she knows that it was a lesson learned, she doesn't want him anymore, because she finally knows he used her, and he lied to her. She is saying thanks for the memories because she knows that it makes her stronger.
She's talking about in the beginning how she was upset about it, how she couldn't sleep because she thought about it. But by the end of the song she knows that it was a lesson learned, she doesn't want him anymore, because she finally knows he used her, and he lied to her. She is saying thanks for the memories because she knows that it makes her stronger.