When did you realize your strict startup rules actually didn't work?

I dug up some old notes from when I first started building software, and honestly, reading it made me laugh. Back then I had these rigid ideas about how things "should" be done like refusing to use certain third party tools or trying to code everything from scratch to keep it pure. Fast forward to today and I’ve broken almost every single one of those rules just to survive and actually ship things. The market teaches you pretty fast that idealism doesn't pay the bills.

Have your early business rules survived contact with actual customers or did you have to throw them out too?