To undercut or undermine someone's dreams or aspirations.
sweet dreams
Said to someone before they fall asleep, wishing them a good sleep.
soften someone's cough
To completely negate or undermine someone's argument or position on a …
cut down the tall poppy
To belittle or undermine someone who is perceived as superior or more …
yellow brick road
A proverbial path to a Promised Land of one's hopes and dreams.