Oh, sleep, one of my most favorite activities. Except for the months leading up to the separation from my first husband, I have always been a world-class sleeper. No matter what the worries and stresses of the day, my head hits the pillow, and I am out. I do realize what a blessing this is, and I am very empathetic to the many people who have a different experience.
During cancer treatment, it is especially important--and often especially difficult--to sleep. Nothing goes well if you are exhausted. Everything is harder if you are sleep deprieved. This is a quote from a good article about this problem from Cancer Net at ASCO and then a link to read more. Note that there is both a written summary and a podcast (you have to scroll down quite a bit to reach the material):
Many people living with cancer experience occasional sleep difficulties; for some, sleep is a nightly challenge. Disruptions in sleep patterns may stem from physical side effects of the cancer or cancer treatment, or from stress and anxiety. Talk with your health care team about any sleep problems that you experience to determine whether any adjustments should be made to your medical treatment. In addition, some simple changes to your daily habits, sleep environment, and stress level can make a big difference in the amount and quality of your sleep and, ultimately, in your quality of life.