Hello. You did not say what text the question is referring to, which will make the answer inaccurate, but I hope it helped you.
Santiago says that the idea emitted beforehand scared him because it was a different idea than he imagined and that confronted what she believed, or even, that generated a very terrible result and that was far from what he wanted to do or that created a more harmful than he imagined.
Anyway, the idea was something that caused him fear, anxiety and fright, either by execution, or, by the result.
