This was the best advice I received and I am going to pass it onto you. Be kind to yourself, throw the idea of healthy eating out the window until after you get through chemo (chemo is doing much worse things to your body then a block of chocolate will ever do), it is just one more thing to beat yourself us about. Eat what you want, when you want even if it is chocolate for breakfast.
THEN, when chemo is over get back into your healthy eating, but for now just concentrate on getting through it. I lived on red softdrink, salt and vinegar chips and avacado on toast with lemon?? Go figure, but I am happy to report back 5 years that when chemo finished I got healthy and am still eating well.
Good luck.