let yourself go

Từ điển Oxford Advanced Learner 8th

ˌlet yourself ˈgo idiom
1. to behave in a relaxed way without worrying about what people think of your behaviour
•Come on, enjoy yourself, let yourself go!
2. to stop being careful about how you look and dress, etc
•He has let himself go since he lost his job.
Main entry: ↑let_idiom