free rein idiom
（言行或情感的）自由，自主，无约束
the freedom to do, say, or feel what you want
The young film-makers were given free rein to experiment with new themes and techniques. 年轻的电影制片者们对新主题和新技巧可以自由尝试。
He deliberately gave his emotions free rein as he played the sonata. 演奏这首奏鸣曲时，他刻意使自己的感情尽情奔放。