Parentheses have an unfair reputation for containing the optional part.

Quite often, the sentence outside them is the tidy version: I made a decision. The bit inside is where the writer admits the decision took three attempts, two detours and one period of pretending not to care. That’s not optional. That’s the part that lets me believe the sentence.

I like parentheses because they can hold a correction without turning it into an announcement. A dash makes an entrance. A footnote sends me elsewhere. Parentheses just make a little room beside the main thought and let the awkward detail sit down.

They can become a problem, obviously. Put parentheses inside parentheses and the sentence starts carrying emergency exits. At that point, the aside has won. Give it a sentence of its own.