Maybe it helps that my eyesight is really poor. As I can't see much without my glasses anyway, turning out the lights takes little away.
I know where my washcloth, shampoo, and soap are located. I know where the shower controls are located. I turn on the fan, turn out the light, walk into the tub, draw the curtain, and turn on the water, adjusting the temperature before switching it from the tub spiggot to the shower head. I shampoo, rinse, scrub my body, rinse, and spend probably way too much time enjoying the warm water flowing down my body. No one disturbs me, usually. When I'm through, I turn off the water, grab my towel, and dry myself. Once out of the tub, I turn on the light.