" The only thing worse than not knowing why some code breaks is not knowing why it worked in the first place! It's the classic "house of cards" mentality: "it works, but I'm not sure why, so nobody touch it!" You may have heard, "Hell is other people" (Sartre), and the programmer meme twist, "Hell is other people's code."
I believe truly: "Hell is not understanding my own code. "

― Kyle Simpson , You Don't Know JS: Async & Performance