One of the hottest things a man can say is "No."
No, you don't have permission to drink caffeine.
No, you are not allowed to skip your workout today.
No, you can't cum this week month year.
It reminds me that he is in control. That my range of available actions depends on his permission and that getting his permission is a privilege - not a right. The constraint makes me feel so safe. A man who is strong enough to say "no" is a blessing.