So if introversion is some strong social anxiety, and you have one bad social experience at a bar, it could just reinforce that anxiety out of proportion to the actual reality. The brain isn't always rational unfortunately.
But I don't think introversion and social anxiety is the same thing, though I absolutely buy that they probably often co-occur. To the extent I have any social anxieties, they are very specific and limited, and don't really affect me much, but the energy drain of interacting with people does.
I tried this - I forced myself into social situations daily for years, and kept a log to make sure I could guarantee that I actually did. It did make me far more comfortable, but it did not at all affect my energy levels.
I think comfort is probably necessary to maintain your energy, but not sufficient.
In the end I stopped because it made me miserable and tired. I don't regret having spent some time doing it, and I learned a lot, but it certainly did not change my introverted nature.
I'm sure to some people it's about comfort levels, and so I'm not suggesting it can't work, and it's probably worth trying for people who feel socially awkward. But for me the main thing it taught me was that I don't want to be a social person.
Merely exposing yourself to a situation again and again will lessen your anxiety and put the kinds of automations in place, in terms of perception and behavior, that will make you feel “comfortable“ (i.e. allow you to handle the baseline situation on autopilot, so your energy is free for higher level functions, such as strategy or simply enjoyment).
This means that, being an introvert, you can make yourself tremendously more comfortable in extraverted [1] situations simply by going to a bar or a coffee shop twice a week and spending time there. Simply being there slowly gets you used to the environment. (It’s very similar to desensitizing a dog to fireworks, for example. Sorry! :))
Also, I suspect this is what actually creates these differences in personality types in the first place. Some people get really comfortable being by themselves, and others get really comfortable being around others. It starts in early childhood, and becomes a self reinforcing cycle. In many ways, it makes sense to do more of that which you’re already good at. Changing your environment is often more profitable than trying to change yourself.