Don't beat yourself up because you didn't eat as well as you wanted on two days. As I tell all new members and those looking for motivation,"don't look at good health with an all or nothing mentality". If the only healthy thing you did for yourself today was drink 8 glasses of water, that's still a step in the right direction.
You don't have to be perfect every single day. Every little bit really does make a difference. I'm glad you're going to keep fighting the cancer. Having a positive attitude will help you beat this disease.