fling your cap over the windmill
fling (one's) cap over the windmill
To act in a deranged, reckless, or unconventional manner. Refers to the eponymous character of the novel Don Quixote, who tosses his hat over a windmill (which he imagines is a giant) as a challenge to it. Sarah is always trying to buck social conventions, flinging her cap over the windmill whenever possible. I know you like to take risks in business, but don't fling your cap over the windmill.
fling (or throw) your cap over the windmill(s)act recklessly or unconventionally. dated
1933 John Galsworthy One More River I suggest that both of you felt it would be mad to fling your caps over the windmill like that?