There's a specific kind of exhaustion that makes you into a person you don't quite recognise. The person who snaps at their partner for asking an entirely reasonable question. The person who cannot make a decision about something small and feels genuine distress about it. The person who is made furious by nothing specific — and then made worse by noticing they're furious about nothing specific. She is not difficult. She is running a nervous system under neurological constraint.

The first time, I did not know what was coming. They operated on bones in my foot. Gave me a spinal block. When it wore off, they asked me to walk — on crutches, on the foot that had just been cut open. I made it a few steps. And then the world went black. Not metaphorically. I literally fainted. From pain. That was surgery one. There were three. And there is a fourth I need — and cannot make myself do. It has to do with a specific molecule in the neurons of my spinal cord. Once you understand what that molecule does, the fact that I cannot walk back into that operating theatre will make complete neurological sense. It is not a failure of courage. It is a consequence of learning.

Everyone is told to lower their cortisol. Nobody explains what cortisol actually does — or that in the female body, it follows a measurably different pattern across the menstrual cycle, interacts with estrogen through two opposing receptor pathways, and was excluded from stress research for decades because its variability was considered a confound. That variability is the biology.