As the preacher said, a surprise is better than a promise fulfilled by God. A promise fulfilled by force doesn't have value. It felt like the person was too eager to get it.
I remember some time ago, a friend of mine promised to send me money. So with my canal mind, I use all my money since I'm expecting money Na.. but to my surprise, the day dawn, and I never saw anything from him, he didn't even mentioned it.
Days turned to weeks and weeks tuned to month. Nothing to show. I struggled to settle my bills that period since I did impulse buying, thinking something bigger is coming.
After some time, I decided to remind him of the money and he got pissed up and send the money.
But then, I didn't need it anymore. I had to refund the money back to him.
Unfulfilled promise can lead to a broken relationship, even with your children. Because the other opponent feels, you didn't meet up her standards and that might lead to depression.
It is better we surprise than being forced to fulfilled our promise.