Do you write backstory ideas for your characters down?

I do.
Sometimes, they’re really awful. Sometimes, they’re pretty good. Mostly I wind up not using them. The below was for a character in a short story I wrote. I didn’t use any of it, but I really liked the imagery in this piece.

“Sera”

There had been better days, she knew. A time before violence was commonplace. Now, it seemed to be the only currency that people understood or accepted. She thought back to the wet, green rice fields surrounding the tiny village where she’d spent her teen years.  There had been a small monastery at the outskirts. Monks with shaved-pates and flapping orange dhoti had wandered the muddy streets, offering manual labor to any who needed help. They didn’t ask for anything in return, simply smiled a gapped smile and moved on to the next villager. She’d once helped them to remove a recalcitrant nanny-goat from a tree. Frightened by the backfire of a passing truck it had ninja-jumped from feeding trough to the tree. The poor thing had been bleating and peeing in her distress. The monks had just laughed and joked about the situation. A goat in a tree! They had laughed that goat down and into her owner’s arms.