If you are hungover then this means you consumed too much alcohol previously, and know you are paying for drinking to excess. You may feel weak, a headache is common, and many people feel nauseous or sick to their stomach as well. This is your body's way of letting you know that you went to far, and it will take your body some time to recover. If you wake feeling hungover then fluids are important, because part of the problem is dehydration from all the alcohol.