When I was single and living by myself a long time ago, that did suck. But going out to bars and drinking is not the only way that people can socialise. There are all sorts of special interest clubs you can get involved with (for me, gaming clubs, going to church and volunteering at a youth club were some of my social interactions outside of work).
Plus, there's more than just IRL friends. Internet peoples can be friends too
p.s. The trick about being 'upbeat and interesting' is that you can totally rehearse that. I got bullied a bit when I was at school and developing clever or witty sayings can take you a long way in social situations. Even something as inane a 'not bad for a saturday' is better than awkwardness. One that I cam up with as a way of breaking past the banalities or talking about the weather (I *hate* that sort of insubstantial conversation) is to come up with alternate wordings for things that don't trigger people's automatic responses. For example "What's happening in your world today?". Or you can pretend that that's the question when people are asking you.
Thinking like that can get to be a habit and can be an easy way of casually showing to other people how awesome you are