The phrase "bent up on" implies strong commitment or determination towards a particular goal or objective. Antonyms for this phrase would be "relaxed," "carefree," "unconcerned," "apathetic," and "indifferent." These words suggest a lack of interest, dedication, or passion towards any specific outcome. They are often used to describe a person who is not invested in a particular task or does not consider it important enough to prioritize their time and energy towards it. Being "bent up on" about something can be positive, but it can also be negative if it leads to obsession, inflexibility, or neglect of other important aspects of life.