Antonyms for "make oneself at home" include feeling uncomfortable, being unwelcome, feeling out of place, and being a stranger. If you are hesitant or uninvited, it might be difficult to settle in and feel at ease in a new environment. Similarly, in formal settings, it may not be socially acceptable to behave as though you are already familiar with the surroundings. Instead, you should aim to be respectful and observe the etiquette of the place. In situations where you are unfamiliar, it is always better to err on the side of caution and wait for an invitation before making yourself at home.