1) If I cancel the concert, mentally I will feel very bad.
2) If people are so kind to come to listen to my concert, I absolutely cannot be unprepared, otherwise I will feel very bad. I just don't like to feel myself bad, so I have no choice, but to be prepared, and I know, for me it takes that much time.
I know what you mean. When I play for an audience, I feel that my performance is there for the audience to see, to judge, so I try my very best to come on time, dress my best, play my best, etc. And although I've come many times close to cancelling, I never have cancelled.