The terrible thoughts of loving someone

Ever since we moved to the sixteenth floor we have both had nightmares/horrible thoughts. John is afraid of heights and even though I am not he rubs it off on me. When Ymir moved in the dreams/thoughts include him as well. They go something like this:

I stand on the balcony with my back against the railing. Suddenly I tip over like my head is heavy and my feet lose connection to gravity. I fall heads-first.

A variety of this is that I am stupid enough to sit or even stand on the railing and fall.

With Ymir it more like this. I hold him in my arms and go close to the railing, showing him the view or wanting to take a photo of him. He starts to twirl and leaps from my arms over to the other side. I watch him fall sixteen floors.

Variety: I leave the balcony door open and when I come back from where I were I see him standing on the railing looking at me. Slowly I go nearer, talking to him and trying to make him jump down and come to me. When he turns to do so his paw slips and I see him fumble and fall.

Please tell me how to get rid of these life-threatening thoughts. They are keeping us from enjoying being on the balcony. I can not lean against the railing without feeling like I am about to fall. I can not lean against it when John is home, he will drag me away from it with a worried look. I can not sit on the balcony reading while Ymir is there since I am too scared that he will magically jump so high up and over if I look away.

But hey, at least the view is great!