Is it considered appropriate in Islam to make decisions based on visions, such as a terrifying vision that led to ending something, and can one be certain that it is not from Satan?

It is not possible to definitively rule on dreams, as it depends on the state and actions of the dreamer, and the type of dream itself. People in this regard fall between two extremes and a middle ground: some do not care about dreams, others exaggerate their reliance on them, while moderates benefit from them to an appropriate extent. There are many errors related to dreams and their interpretation, including: neglecting them, interpreting them ignorantly, failing to distinguish between their types, deriving rulings from them, being lenient in interpreting them without knowledge, interpreting them without knowing the dreamer's state, not differentiating between a vision (ru'ya) and a dream (hulm), and prioritizing them over istikhara (seeking guidance from Allah).