Being on one case can be a demanding and stressful task, as it requires one's undivided attention and focus. However, the antonyms for this phrase could lead to a more relaxed and peaceful state of mind. One opposite of being on one case is being carefree, which means to be untroubled and without worry or responsibility. Another opposite is being at ease, which refers to a state of being relaxed and comfortable without any pressure or tension. Lastly, another antonym for being on one case is being detached, implying a lack of emotional involvement or concern. Nonetheless, these three antonyms could also indicate a lack of productivity or effort to accomplish a task, unlike being on one case.