At university I had a professor who would jokingly refer to his Law of Conservation of Misery:
The total amount of misery in a system is constant
which implies that when you try and decrease the misery in one aspect of a system, you will increase the misery in some of the other aspects.
There are many types of misery. In software engineering projects these could include non-maintainability, non-performance and budget constraints.
Personally, I think people are too prone to think that there are zero-sum monsters lurking under each bed, so my own take on the "law" would be:
The total amount of misery in a system is > 0
Which implies that you can make tradeoffs that decrease the total amount of misery, but you can never eliminate it completely. A bad implementation of a system will have a higher total amount of misery, and a good one will have less, but you will always have at least a little bit!