One day at a time is the way to go. No matter how crappy you feel, and apparently some people don't feel too bad, just remember you can do this. It will come to an end. When I was 2/3 of the way through and hurting my radiation oncologist told me "hey you are almost there it will be done before you know it".

Find something to distract you during the remainder of the day. I was able to telework part-time which helped a lot. Sleep and get your nourishment as that is critical to being able to maintain a healthy mental state. Try and minimize the pain from the mouth sores. Viscous lidocaine, glutamine - I used a product called Healios which worked well. Remember that if you are in pain it will negatively impact you mentally.

Take advantage of days where you feel good. Enjoy your weekends if you are on the 5 day a week schedule.