Blow off steam

Although this expression goes back to steam engine days when a relief valve would control excessive steam pressure. Today it means to blow off excessive energy or emotional excess like anger or boredom. When someone is kept idle too long, or feels encaged, entrapped they want to 'unwind', to blow off steam.
Children at recess are blowing off steam so they will be attentive in class.

Βγάλτο από μέσα σου

давать выход избытку энергии; дать выход чувствам; "выпустить пар"