The antonyms for the phrase "exerts oneself" would be terms that describe the opposite of putting in effort or working hard. Some antonyms for the phrase might include words such as: slack, idle, laze, loaf, relax or procrastinate. These words all indicate a lack of motivation or willingness to work on something, which is the opposite of the phrase "exerts oneself." Furthermore, antonyms for the phrase could also include terms like "takes it easy," "coasts," or "chills out." These all describe a more relaxed or lackadaisical approach to any given task, which is diametrically opposed to exerting oneself.