Hi, Prudence. How do you get to the place where you'll be able to let go of your fears? Well, I think you're already there. Your whole post is about it. You know it's the right thing to do, for both of you, you are just afraid, and you recognise that your fear is just an illusion.
My only advice as to how to overcome that fear is to observe it
. The nickname you gave to your partner reminded me of a boat-related story - I once went with my husband on a week long boat trip on a river. One night there was a huge storm (later we found out it totally devastated the area), during wich we were moored by this concrete wall far from cities or camps. Our boat was small, so all I could do was lie down in the cabin, next to my husband (who was perfectly calm). I was completely paralysed with fear. We were tossed up and down and sideways in alarming angles. I was so afraid we would get smashed against the concrete wall, or that the lines would snap and we would end up going over a weir somewhere. But because there was simply nothing I could do, I started to analyse my state. "Look at her, she's so scared, the poor thing," I thought about myself. "Her throat is constricted. She doesn't breathe very well. Her limbs are all tense."
This helped me to distance myself from the fear. It was, after all, just an illusion serving no purpose. Miraculously, I calmed down, and just waited it out.
So that's my advice. You know where you stand, you know the risks, you know the benefits. Your fear serves no purpose anymore. Watch it, write about it, say it outloud, and it will go away. There is always some measure of momentum with our fears and insecurities, so it might take some time. But it will