The phrase "lit up on" typically refers to feeling excited or enthusiastic about something. However, there are several antonyms (words with opposite meanings) that could describe a lack of enthusiasm or excitement. Some possible antonyms for "lit up on" could include feeling bored, uninterested, disenchanted, uninspired, or apathetic. These words might apply to situations where someone is experiencing a sense of low energy, indifference, or even disappointment. While it's natural to feel less excited about some things than others, it's important to stay engaged and open to new experiences to keep our minds and hearts "lit up on" the things that matter most.