Unfortunately, sometimes the best laid plans need to change. If you are no longer able to make your appointment or you need to re-schedule, as much notice as possible would be appreciated for several reasons.
Firstly, it allows me the time to contact another client that may be waiting. Secondly, it gives those clients on a waitlist time to make the necessary plan to attend an earlier appointment. However without due notice this does not happen and others lose out.
The same applies if you are unwell, please stay in bed and recuperate but do try and give me at least 24 hours notice.