What geekette and pk_aeryn said. I have reactive hypoglycemia but not diabetes, and I generally get 'crash' symptoms if I eat sugar or simple carbs with no mitigating protein or fat to slow down my insulin response. I react both to low blood sugar by itself (anything be below 70 for me is not great) but I react most strongly to a sudden drop in blood sugar. In other words, my bs can be technically fine (e.g., 85), but if it's dropping rapidly off a spike caused by too much sugar or simple carbs, then I get symptoms just as bad or worse than when it's just low but stable.
The problem is that it can become a cycle where you crash, crave sugar and carbs, over-eat them, spike your insulin and blood sugar, crash again, etc.
The way off the merry go round is to cut WAY down on all sugar and simple carbs, and eat fiber, protein, and healthy fat with the carbs you are eating. Eat a small amount regularly throughout the day.