If you can, try to avoid ruminating over this. It is a vicious cycle once you enter it.

In my case I forced myself to get out. I also forced myself to contact acquaintances - even those I had lost touch with. This seemed like such a daunting task to me. I was Anxious as it put myself at risk of rejection. But this never happened. I still keep myself at arms length away but the loneliness was abated. I happened to meet someone because I reached out.