Wiktionary
shape up or ship out
vb. (context idiomatic English) To either improve one's behavior or else be required to leave; to either improve one's performance in an activity or else withdraw from that activity completely.
Usage examples of "shape up or ship out".
This, they mean, indicates I am an oddball and had better shape up or ship out.
Her behavior had become unacceptable, and I told her to shape up or ship out.