At the end of the day, when you are emotionally drained and aren't really walking around smiling or in a good mood (although you're not in a BAD mood either), it doesn't mean you have dropped in your spirit.
Sometimes our body becomes tired and emotionally drained, but it does NOT mean that you're in a wrong state before God. It is completely okay to be emotionally tired. HOWEVER, if you mistaken your state and start listening to what your body wants in order to make itself happy, and those things do not align with the desires of your spirit, then you are in trouble. Also, if you become easily irritated and your emotional state begins to affect your spirit, you are also in trouble. You will end up doing fleshly things which seem to make you happy in your emotions, but they leave you spiritually empty, and as a result you'll feel drained in your emotions AND your spirit.
When you are emotionally drained, in order to counter it correctly, you must simply look into your spirit and ask yourself "What does my spirit want at this moment?" Or "Lord, I am emotionally drained, what should I do?" And sometimes in your spirit God can call you to go for a walk in the park and rest in Him, or perhaps go to sleep, it really depends. What is essential is that you don't consult with flesh, but you consult with the spirit, and do what he tells you.
I believe emotional drain is the exact reason Jesus went to the mountain to pray. Prayer doesn't mean he was standing on his knees all night calling out to the Father (the way it is often preached), but rather, he just sat there, looked at the stars and the nature around him, and his heart was filled as he took in the glory of the Father and his heart united with him. I'm speaking from personal experience and don't claim to know what exactly he did there, but that is how I experienced it and see him doing it.
Do not let your emotions affect your spirit, but rather, consult with your spirit and do what it tells you despite how you feel in your emotions.
May the Lord bless you! :)