Sarah laughed when God said she’d have a baby. He didn’t cancel the promise; the kid’s name ended up meaning “he laughs.”

Hearing something too good and laughing at it is a reasonable response to an unreasonable claim. The story does not punish the laugh. It folds it into the result, so that the thing she doubted ends up named after her doubting. Scepticism is not disqualifying, and it is not the same as refusal.

Where you half want something and mostly disbelieve it, you do not have to produce confidence you lack. Say the honest version out loud, including the part that finds it ridiculous. Then take the next step as though it might work.