I checked the "fall off" in Longman Dictionary, it means:
if part of something falls off, it becomes separated from the main part
if the amount, rate, or quality of something falls off, it decreases
somebody nearly/almost fell off their chair
But no one fits with the phrase.
So, could you please tell me what the meaning of "I’m done falling off shit" is?
The text is:
Construction began on the milking barn in Oneida. Shawn designed and welded the main frame—the massive beams that formed the skeleton of the building. They were too heavy for the loader; only a crane could lift them. It was a delicate procedure, requiring the welders to balance on opposite ends of a beam while it was lowered onto columns, then welded in place. Shawn surprised everyone when he announced that he wanted me to operate the crane.
“Tara can’t drive the crane,” Dad said. “It’ll take half the morning to teach her the controls, and she still won’t know what the hell she’s doing.” “But she’ll be careful,” Shawn said, “and I’m done falling off shit.”