No I don't view being afraid as cowardly....doing what you need to do is difficult as all get-out!!! BUT..you've got to get past this. Truly, when I first started having these difficult talks with my H my heart was pounding, my hands were sweating and I could barely find the words. I was sooo scared what I was going to say would piss him off or that he'd simply walk out the door never to return. The ironic thing is he thought having those talks was easy for me...because I was always the one to bring things up, because he wouldn't.
Finally, one day we had a little talk that kind of just happened. I told him that a talk we had the previous night, that started with an e-mail was really hard for me. He looked at me like "why?"....so I sucked up the courage to tell him my fears. When I told him my fear about him leaving he quickly said "Oh NO! That's never going to happen!!, I know a good thing when I have it!" So we literally came to an agreement that neither of us were going to go anywhere...we are in our M to stay. Part of that conversation was me telling him that if I have a problem, or I have something on my mind he's going to hear it....he agreed, and we actually came to an understanding that no matter what either of us might say, it might tick us off, it might hurt our feelings, whatever....we'll both get over it and still be there for each other.
Perhaps you need to open up a conversation with your W about how afraid you are to bring up these things with her...because of...xyz. It's worked for me....my H and I can now talk about ANYTHING. True, I may be the one to still bring things up....but he's getting better, he's starting to stick his toe into that "iffy" subject matter pool too.
As hard as it is...and I repeat your aren't cowardly, just scared...you do have to work past this communication issue. Communication, I truly do believe, is at the heart of some of your issues.
You CAN do this, and you aren't alone in your struggle to get past it...and feelings are a hard thing to communicate; they make us most vulnerable to others. A letter in your instance might be the best place to start. And if you feel you have to repeat what you wrote earlier, then do so