Donald Knuth famously said:

The real problem is that programmers have spent far too much time worrying about efficiency in the wrong places and at the wrong times; premature optimization is the root of all evil (or at least most of it) in programming.

You’ve either a) learned this lesson the hard way, b) learned it the easy way (by listening to others’ tales of woe), or you c) should learn it now alongside Victor Zhou as he recounts how he ignored Knuth and wasted a lot of time because of it.