Never, ever try to thin chocolate with milk, juice, or liqueur unless you’re making a sauce. That will cause instant seizure and you’ll have to start over. Also, resist the urge to blast it in the microwave—that just burns the cocoa butter.
And please, for the love of sugar, don’t throw the seized chocolate away! It can be melted back into brownie batter or used as a topping for ice cream. Waste is not an option in the chocolate zone.