If you are feeling stressed, overcommitted and worn down, I am going to encourage you to take a look at your schedule and, more importantly, how often you are saying "yes" to things out of obligation, guilt or fear.
Feeling angry can be beneficial to a person with cancer. It provides a means to vent and let off steam. After all, if anyone deserves to feel angry, it's someone with cancer. I believe it's even essential to feel anger in order to "process cancer" -- just not all the time.