To leave someone alone with their emotions, usually unpleasant ones like guilt, anger, or anxiety, without offering them comfort or closure on the matter. Kevin was in such a foul mood at dinner that I went home early and left him to stew in his own juice. After the kids broke the window, I left them to stew in their own juices for a while before laying into them about it. I can tell that the boss is upset with how my report turned out, but I think he's just leaving me to stew in my own juices about it before he brings it up.