Generally I say: "let's make a good effort, to not let a bug pop-up on the user's face." Hehehe.
Particularly, I love documentation. Doesn't need to be a gigantic comment at the beginning of each function/method, but the Business Rule that the code is about, must be explained. Without this, maintaining and improving a code base for whatever service, might be a 'seek 'n hide' + 'riddle' game, and to be honest, I don't like it, at all.
Logging is a good thing too, essentially, if the application is on debug mode. Makes life much easier for gigantic code bases.
Since a gray-beard guy mentioned these four, they make more sense to me, who have a black-beard, yet.
Runtime errors are better than bugs
Tooling is better than documentation
Documentation is better than nothing
As a grumpy old gray-beard those four are my favorites