Best time to cancel? / help with canceling

Hi! I have decided I would like to stop receiving my glam bag each month. I want to receive my December bag and all the add-ons I picked, but I want this to be my last bag. When is the best time to cancel? Should I wait until my December bag has shipped? If they made any mistakes on my bag will they still fix them if I cancel my subscription?

Also, any advice for canceling from people who have before? I haven’t looked into it yet on the website but I’ve heard they don’t make it easy!