I got on and started walking, trying to give him things to do while avoiding the spookiest area (the long side around B). After about 10 minutes I got him trotting on a circle in the far end, which tends to be the least spooky area. He was pretty tense throughout, especially on the quarter of the circle closest to the scary side so I tried to do smaller circles before we hit that to keep his attention on me. He was very tense and tight, so mostly I was just trying to get him moving forward.
He did once respond to my leg by kicking out, but I mostly ignored that pissy moment.
I continued avoiding around B, so I would ride down the opposite long side, turn onto the centerline at C and angle back to K, or do shallow loops or other figures trying to avoid the spooky side.
We did a little cantering also on a circle at A. Cupid rushed a bit, so I just tried to remind myself to keep sitting back like I've been doing.
Finally we walked down the spooky side, at first halting a few times. Cupid had his head up high and was looking around, but at least walked straight. Then we walked down it without stopping, with a bit of shoulder fore to the inside. Then when he trotted straight down, I decided to do a quick stretchy trot and end it on a semi-good note.
It can be a bit frustrating, he's been so good out there I thought we were finally over this. But later when I told my friend who boards at the same barn, she said her horse was pretty up on Sunday too (though she didn't ride in that arena), so maybe it was just something in the air!