Which is not the same thing as being alone.
I love being alone; crave it, actually, as it helps me recharge my own emotional battery. Lonely is totally different, it feels like no one has ever loved you or ever will.
When I feel lonely, it hits me whether I am by myself or surrounded by a dozen people. It is not a good feeling, it makes you feel insignificant and small.
This type of mood hits me very, VERY rarely. And it passes very, VERY quickly.
But it is horrid while it lasts.