Day 239. I have one last packet of dry rations and one square piece of chocolate left. I could try to stretch it out for four days. Or I could eat everything now, so that at least today I can sleep without stomach pain. So that's what I do, after settling down on my bed.
Tomorrow I will wake up, go about my usual day, send my last message to Earth, and inject myself with as much painkiller as I can before I lose consciousness.