I agree that the thoughts and feelings of other people in general are difficult to predict. But a person you marry is often someone you spend a lot of time around and hence whose thoughts and feelings can be predicted to some extent - because you see them in different situations, then see their reactions and talk to them about their thoughts and feelings.

In this specific case, the author denies that the consequences existed:

> But that doesn’t make sense, I thought. I’m not trying to hurt her; therefore, she shouldn’t feel hurt.