flailing & failing

I can't write your letter. My thoughts have been translated into full and well structured sentences in my head. But now, I can't write your letter. The uncertainty of it all is holding me back. Maybe it just means that I'm not ready. Not ready, that should be the title of the book I'll write about us one day. Not ready to let go in every sense.
Why can't I just write to you like I used to - why are things so different now?

I feel like my heart is in a vise-grip and the more I try and put the pen to paper the tighter my heart is squeezed.

I know what it must seem like, probably even more so now after reading this mess. The truth is, my struggle lies more in who your letter is from - as in which part of us (part of me) wins and gets to hold the pen.