How to be alone without feeling lonely?

Title, really. Went to Sakura-Con today (I've never been to a con, wanted to go to one for years), and it made me feel more lonely than I usually do.

Never had friends, family doesn't like being around me, never so much as hugged a girl or been on a date, nothing -- never even had internet friends in my 14+ years of MMOs.. As you can imagine, that's not a lot of fun. But, it's obviously not going to change any time soon, seeing as it's gone on for 23 years now.

So, without the whole sob story, how can I be alone without feeling lonely?