I was in exactly this position two years ago. Exactly. I knew I had to come out as the first step in a transition that I had to do. It wasn't really how to come out that was the hard part: obviously the how was to say, "Sweetie, I'm transgenger." The hard part was how to get past the fear that was preventing me from doing it.
It literally took me months to get past the fear. So many times, I thought, "Now is the perfect time", I'd draw a breath, get my lips and tongue in position to speak the first syllable, and then freeze in a panic attack. The words literally would not form in my mouth.
I kept at it. The repetition built up a layer of self-loathing that I don't recommend, but which helped motivate me to eventually do it. If I hadn't done it, I would have hated myself so badly...
I also contemplated, especially after each failed attempt, what my life would be like if I didn't come out: a gradual downhill spiral of frustration and cowardice, with an added garnish of fresh self-loathing. I saw myself as a bitter old man, pining for the happy life that might have been. And I knew that only I myself would be to blame for that fate.
That was not a pleasant thought to contemplate, but it did help get me motivated. I compared that future to the possible futures if I did come out. I had faith in the good character of my wife, and knew that there was a good chance she might stay with me. And that, if she left me, we could probably come to an amicable agreement.
I finally ended up giving myself a "mantra" to recite: "Gotta do it." I'd be out there on our daily dog walk, and, in my mind, I would be repeating, "Gotta do it. Gotta do it. Gotta do it." I rehearsed (many times!) the exact words I would say. Finally, the repetition got to me, and I did it. In a strange, detatched state, I heard my own voice say the words, "I think I am transgender." It wasn't my imagination: I really did say it.
I get it that it is hard. It was probably the hardest thing I have ever done in my life, and I've done some difficult things. It felt like jumping out of an airplane without a parachute. But by that time, I knew that I could not survive with any degree of sanity if I didn't do it. I just had to trust that my wife could catch me.
And she did.

I have no idea if that is helpful to you. The demon you face is internal, and ultimately, you have to face it alone. That is how I did it, and it was the turning point in my life.
Good luck!