We may crave time alone the way we crave time with others

When we feel lonely, it's because our desire for company exceeds our ability to find it. This process can work in reverse as well: If our desire for solitude exceeds our ability to find it, we can also struggle with feelings of discomfort.

"If we're not satisfying that need, there might also be a cost, just like there's a cost of being lonely if you don't satisfy your need to belong."

What constitutes the right amount of solitude varies person to person, Coplan says, but when you aren't getting enough time on your own, you may begin to feel more irritable, anxious or put out.