your energy is affected by your liver... which affects your adrenal glands. If you have eaten sugary foods... caffeine or other stimulants... or just stress you could be hormonally underbalanced.

The quickest remedy i know if is bieler broth which takes potassium rich vegetables such as zucchini.. and steams them and you eat that for a few days. Then you must work out a decent and better diet because most likely what you are a feeling is the result of what you have consumed. you are what you eat.