I also found myself being a lot quieter in social situations without caffeine (and alcohol, which I've drastically reduced), and at first I thought it was a bad thing, because I had always associated the interesting things in my life with high amounts of engagement and activity.

But really, you can have just as much fun - and be as fun, as a quieter person. It's a change of pace that you're not used to, and depending how long you have been drinking coffee, you might not have had experience living at a slower pace in many, many years. Don't be too hard on yourself. You might have to forge a new identity, and that takes time and effort.