I'm still fairly new to FFXIV's groups gameplay, but I experience the same thing, except it started out as the opposite, I couldn't help but think about how great I was actually performing...until I started noticing that maybe I was doing too much.

This feeling started to transform into self-doubt. Am I doing something wrong? I'm not experienced enough to notice all the mistakes that everyone makes yet so when we wipe I can't help but think it's my fault. Turns out I just get unlucky with less experienced groups. (Not that it's a bad thing in itself, but it does bring up questions about self-performance at times)

To answer your question, you are definitely not alone in this