Why do we get emotionally drained?

Emotions are a curious thing. We, as humans, are all emotional creatures, whether we would like to admit it or not. Feelings are much like a cup of water. When we give out emotional energy, we need to get some back over time so that we do not end up feeling depleted. We, as humans, attain this energetic refill in different ways. Some folks need to be alone, while others need human interaction. We all reside on a spectrum here because we all need some alone time, and some time to interact with others, the quantities that we need can vary greatly.