I'm fascinated by how aloneness can be so wonderful for some people and so not-wonderful for others. Clearly, loneliness and solitude sit at opposing ends of the being-alone spectrum.
When people think of being alone, they typically think of physical isolation from other people. But it's not the only type of isolation that comes with being alone. How do I know this? Because the times when I have been most lonely in my life were times when I felt alone in the presence of other people. There's a lot to be said for mental isolation. Though I can be in the physical presence of another person and engaged in social interaction, if that social interaction is unfulfilling, then I feel mentally alone.