How does the author use metaphor in the book, In Love: A Memoir of Love and Loss?

One example of metaphor can be found in Amy's utilization of ocean waves as a metaphor for the grief she felt when Brian’s cognitive function declined so obviously. Amy always imagined waves of grief to have actual ebbs and flows the same way the ocean does. She was surprised to find that her grief seemed only to flow more and more strongly as Brian worsened. She felt consumed and thrown around by the vicious waves.