let off steam

let off steam AND blow off steam (to do or say something that helps you to get rid of strong feelings or energy.) — выпускать пар; облегчить душевное состояние; снять напряжение; выговориться (контекст)

Example 1: Meetings give people the chance to let off steam if something has been bothering them for a long time. ( CIDI) — Людям, если их долгове время что-то волнует, собрания позволяют выпустить пар (освободиться от тяготящих эмоций).

Example 2: After a long journey, the kids need to run around a bit and let off steam. (CIDI)

Example 3: I've told her she can call me and talk any time she wants to blow off steam. (CIDI)

Related vocabulary:
[take sth out on sb]
[give vent to one's emotions]