Diabetes is one of the leading diseases in tthe modern world and preventing it is probably the best thing you can do for yourself. However, if you already have diabetes, it's not the end of the world, but it should be treated properly and kept under control.
Probably the biggest risk of diabetes is not the disease itself, but the complications that come with it. This especially goes for Type II diabetes. People know they're sick only when they feel these complications and that's exactly why its important to always keep the sugar levels in your blood in check.
The most common complications are hypoglycemia (glucose deficiency in the bloodstream) and hyperglycemia (an excess of glucose in the bloodstream). Both conditions are extremely dangerous and if not treated, can develop into ketoacidosis or hyperosmolar syndrome.