Write slow code now, profile and optimize later is how we got all slow software because second step - optimization practically never happens in my experience.

Along with the heuristic that hardware and electricity are cheap, developers are expensive. That's probably why managers in my experience almost never ask developers to optimize slow code - they believe it would be cheaper to use more hardware if this fixes the problem (in some areas like HFT or GamDev more hardware is not the answer so optimization do happen). In rare cases I've seen optimization being done initiative always come from IC (who knew that the code could work fast / use less resources).

So nowadays writing code I assume that it never will be optimized later and try to do less dump stuff from the beginning.