If my blood sugar has dipped too low (hypo) I can get depressed, hopeless and weepy. And I'm more prone to it when stressed and sleep deprived.
The quickest way I know to feel better is to get my blood glucose back on a comfortable, steady even keel. So I avoid carbs, bread, rice, pasta, potato, fruit and anything sweet and instead I eat meat, fish, eggs, cheese and non starchy veg for a few meals until things steady down.
Your profile says you are type 2, on metformin. Does that mean your doc says you don't need to test?