How can someone feel lonely in the midst of people who love them?

I’m sure some of you—maybe many—have felt this. Standing at a party, surrounded by people and feeling alone. Maybe at a Thanksgiving meal with your family and feeling alone. Or even sometimes with friends or a spouse and still feeling alone.

Do you feel that? Under what circumstances have you felt it? How do you explain it to yourself? What would take away the loneliness? Anything? Or is it just a part of your nature, somehow?