rested on one's laurels

Verb

rest on one's laurels (third-person singular simple present rests on one's laurels, present participle resting on one's laurels, simple past and past participle rested on one's laurels)

1. (idiomatic) To rely on a past success instead of trying to improve oneself further.
   • "Rail has a good basis for promoting green travel options, but we can't rest on our laurels. We need to keep on moving forwards because other modes are upping their games as well," says Brennan-Brown.2020 December 16, Daniel Puddicombe, “Treated DMUs become cleaner and greener”, in Rail, page 47