"Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it." -- Brian Kernighan
Complicated code that isn't easy to maintain isn't smart, it's just complicated. One thing people screw up a lot is implementing some design pattern in a way that ends up shotgunning configuration or business logic over a wide area instead of keeping it in one location and using DRY.
The more magical the code is the harder is to figure out how it works."
A nice formulation of the kind of advice I keep reading here in HN.