Living the social life is exhausting

I consider myself an introvert and I'm trying to make a conscious effort to talk to more people. The other day, I'd say I made great progress and socialized a bit more (which is a big deal to me). But today, I'm just so tired and not in the mood to talk at all. Even smiling was so exhausting, I think I kept a resting poker face throughout the day when I did talk. I even forget to say hi back to people and instead just nodded silently. Eye contact was a bit hard too even though I had no problem with it the other day. I just felt like walking away from class and sit alone till the day ends.

Man, the human brain sure is weird.