Humans are social animals, no matter how introverted. Sometimes it catches up with you.

I'm not quite as bad as the post, but emotions are complicated. I like friends, and I like being invited, even if I might not be able to go.

I do want to go out to places, but sometimes the distance, timing, proximity to last event, etc make it too much.

I don't want to fall out of the list of invitees though, as I will want to go at some point in the future. Sometimes it's an event that not going to might be a problem otherwise, even if I'm not up to it, but to maintain invites/friendship it's best to suck it up.