The antonyms for the word "goes berserk" would be "calm," "composed," "controlled," "level-headed," "restrained," and "sober." These words are used to describe a person who is not overly emotional, impulsive, or irrational. Instead, they are able to stay focused in stressful or challenging situations, make rational decisions, and keep their emotions under control. They are often described as being cool-headed, collected, and level-headed. Opposite to going berserk, they can remain calm and collected, even in the midst of chaos or uncertainty. In short, they are the epitome of emotional stability and balanced thinking.