let it rip
let it rip {v. phr.}, {used imperatively}, {slang}
1. Don't be concerned; pay no attention to what happens.
Why get involved? Forget about it and let it rip.
2. (Imperatively) Do become involved and make the most of it; get in there and really try to win.
Come on man, give it all you've got and let it rip!
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Source: A Dictionary of American Idioms