> Programmers waste enormous amounts of time thinking about, or worrying about, the speed of noncritical parts of their programs, and these attempts at efficiency actually have a strong negative impact when debugging and maintenance are considered. We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil. Yet we should not pass up our opportunities in that critical 3%.

Knuth, "Structured Programming with Goto Statements". Computing Surveys 6:4 (December 1974), pp. 261–301, §1. doi:10.1145/356635.356640

No one has said to ignore optimization, what the quote is actually telling us is to avoid falling into the trap of micro-optimizations which don't really affect the overall performance of the system. Yes, you can spend a week making the world's fastest substring-in-string function, but if you're only checking that your email address has an @ in it, that's kinda silly.

Make your programs fast by concentrating on the areas which give you the most bang for the buck and avoid falling into rat holes where you optimize something which has no impact on the system overall.