One of my favorite quotes:

If the implementation is hard to explain, it's a bad idea.
If the implementation is easy to explain, it may be a good idea.
/Tim Peters, "The Zen of Python"/

"Premature optimization is the root of all evil (or at least most of it) in programming." // Donald Knuth

Преждевременная оптимизация - корень всех (или по крайне мере многих) бед в программировании. // Д. Кнут