Groups – Think about yourself as an observer in the first instance to manage the anxiety, especially with new people, but it’s inevitable that you may not be able to connect to others in that group. Then, there’s the internal dialogue of analysing every interaction you had to sustain during the session, then that all consuming doubt of the quality if you did say something, and how it was noted/received.

Discussions – Fixating on one particular subject that ignites your passion and even your argumentative side in your head, it remains in your head as by the time you have formulated your first word and overcome the inherent anxiety, the topic has moved on.
Breathing – Try to remember to breathe.
Timing – Is everything and it’s never going to be your forte. Accept it. Interrupter extraordinaire, if you do choose to contribute.
NB. All the above is a conversation with myself. Any similarity between anyone living or dead is purely coincidental.