I am almost sure that no matter how 'extroverted' you are, most people would have experienced this feeling. Sometimes we feel lonelier in a crowd of people- precisely because our need to belong to a group. When we do not belong, we feel even lonelier. When you're alone,  such pressures are sometimes alleviated.

 

This, of course, is not a call to distance ourselves from ones who care about you, but a sign that being alone can sometimes be beneficial as well. As much as we are social creatures, occasional lone breaks are very much needed.