Forgetting things

I can understand how upsetting it is to feel you are not in control. But you have had a great deal on your mind, and dropping the ball once may not mean you are losing your faculties! I would hope your husband's work firm would understand a late RSVP in the circumstances. Cancer can certainly dominate your thinking and that's perfectly understandable. Forgetting to do something may also be a subtle hint that coping with a significant health issue is serious work, if everyone is counting on you to do everything you have done in the past, a little reset may be worth thinking about. Don't be hard on yourself, you are coping with quite enough. Best wishes.