Easygoingness, which refers to a relaxed, casual demeanor, can be described by several antonyms. One antonym is "rigidity," which suggests a strict or inflexible approach to life. Another antonym is "tension," which implies stress, anxiety, or discomfort. "Uptightness" is a similar antonym that conveys a similar sense of unease or rigidity. Alternatively, "uncompromising" suggests an unwillingness to adapt to new situations or ideas, while "stringency" implies a strictness or harshness in personal interactions. In contrast to easygoingness, these antonyms suggest a seriousness or severity that can create tension and anxiety in relationships and interactions.