Ronda Rousey Vows to Rebuild Life After 'Rock Bottom'

Ronda Rousey is back on the grid ... kind of ... posting a quote on social media about bouncing back after hitting "rock bottom."

The UFC legend put up a J.K. Rowling quote that reads, "And so rock bottom became the solid foundation on which I rebuilt my life."

Rowling famously delivered the quote during a 2008 speech at Harvard while talking about how she wrote 'Harry Potter' while she was broke, jobless and recently divorced.

Rousey said she was a broken woman after the Holly Holm fight. She appeared to take the Amanda Nunes loss equally hard ... essentially going into hiding after UFC 207 to ponder her future.