Hi ElsaMars, It's good to 'see' you.

Since the mind/body connection is so strong, my first thought is that your mind panics because your body is exhausted. In other words, your mind goes into a fight-or-flight response because it senses that your body is compromised by exhaustion from the shower routine. It seems to me that when my body is very tired and over-stressed, I am more likely to be extremely anxious and then possibly panic. I think this is especially, unfortunately, true when our bodies are sick.

I've used shower chairs after surgery at times in my life and they are very helpful. I hope you get one.