what're some of your favorite personal rules for game-dev?

okay I've got a few:

just because you can make a whole thing in 3D, doesn't mean players have to see every part of it

levels, models, everything. maybe your game is better with a less dynamic camera, or this object doesn't need seconds to load just so it can rotate in the menu

another:

if the player isn't enjoying something, why? is that your goal? if so, why? if you can't answer these questions, you probably need to fix or rethink the thing