"Now, you _said_ you wanted to do this 6-week 5-a-side football course. Keeping commitments is important, you know"
"When someone asks you to do something, there are three possible answers. 'Yes'. 'No'. Or 'I'm not sure, I'll look in my diary' If the answer is one of the first two, you are expected to stick to it. If it is the third, you are expected to return with a reply as soon as possible" (anecdote I heard about what some schoolmaster has on his classroom noticeboard)
Parents often try to hold their children to commitments that they no longer wish to fulfill. Why shouldn't they change their minds? Is there something inherently wrong about rescheduling or crying off entirely?
There's certainly something wrong with simply not turning up when one promised to, because of leaving friends and relatives waiting indefinitely on street corners.
But I think the reason parents are often so pushy about their children honouring commitments is that it is often the parent who makes the phone call to cancel or reschedule, and they are embarrassed. But it REALLY isn't that bad.
One phones the person up and says "I'm so sorry, we can't do it after all" and they say
"Oh, don't worry at all, that's fine, we'll reschedule"
or "Oh never mind, I'll drop the materials off on my way home so you can have a look if you like"
and the metaphorical sun suddenly starts shining. There is something so liberating about being able to change one's mind and say "no, in the end I don't want to spend my time doing what I thought I would want to do". It is important to help one's children have that same freedom.
The bit just before the phone call is ghastly, but it is never as bad as one thinks it will be...