simmer - To heat a liquid, usually a stew or soup, just below the boiling point, allowing it to cook slowly; or to stay in a slow, controlled state of progress or tension, often before a larger event or change occurs.
He was simmering with anger, but he kept it inside and didn't say out loud what he was thinking and feeling.
hysteria - A state of extreme excitement, fear or anger in which a person, or a group of people, loses control of their emotions and starts to cry, laugh, etc.
There was almost mass hysteria when the band played their final song and some in the crowd rushed towards the stage.