I noticed the same effect several times. In my opinion, this happens because alcohol (as already been said) is a drug. Like coffee. It drains inner resources from neural system, to give you temporary boost of energy. If you do not take care of "painless detoxication", by drinking water for example, these energy resources are spent to neutralize toxic effects (to drain water from your body and so on).
By the way, to reduce hangover, it's better to use "sugar water". (The best choise is the honey water with some lemon juice. Add green tea to detoxicate really fast, but make sure your heart and your guts are strong enough to handle it. You may also want to use some "herbal tea" combinations to obtain different effects - ask me for advice
)
The best choice, however, is not to drink at all
If you need "high energy" all the time, there are no shortcuts - eat plants and exercise.
Work your way to energy and good health. Then it would be possible for you to have an energy boost by eating a single fuji apple (like Steve does).
As for me, i'm still in the process of giving up alcohol. But that's the story for another topic...