Bjarne Stroustrup talks, in a good article, about Premature versus Prudent Optimization, which ends up with software design for efficient and maintainable code:
What I don't like is when people, who out of fear of high level features and fear of abstraction, start using a very restricted subset of the language or avoid good libraries in favor of their own hand-crafted code. They deal with bytes where they could just as well deal with objects. They deal with arrays because they fear that a vector or a map class will be too expensive for them. Then, they end up writing more code, code that can't be understood later. That's a problem, because in any big system you'll have to analyze it later and figure out where you got it wrong.
