心血来潮

It was a privilege revokable at any time on whim of the authorities.

这种恩赐权者心血潮随时可以取消。

It was a spur-of-themoment decision.

这是个心血潮的决定。

He flew into a whim and went swimming on a cold winter day, and got a fever soon afterwards.

在一个寒冷的冬天, 他心血潮去游泳, 回就发高烧。