Why don’t I feel more comfortable opening and responding to emails?

When I get a message professionally or personally, I have a problem moving forward and opening it let alone responding to it, if it’s someone that I know. This problem is even worse, if we’re talking about a response to a message of mine.

We’ve been talking in therapy about recording and attempting to better understand when we receive physical signs of anxiety.

For the most part, unless I’m having a full blown panic attack, I don’t really find many situations where I feel like I have physical reaction to my stress or my anxiety. 

At least not consciously.

But when I have a message that I have to respond to someone who knows me or I have to back-up a pointed comment that I’ve made, I don’t know. 

Maybe it’s the same fear that I get around writing in general. Maybe it’s about opening the door wider and letting someone get to know me better.

Why does it feel more comfortable to let it sit rather than respond and engage? What am I afraid of? 

Additional responsibility?

What might be behind Door Number 2?