Behaviour over structure
We, developers, often forget why we even exist.
We quite often don’t remember that our purpose is not to write software, but to solve problems.
Those come in different forms, but can be generalized as “we need to start doing this”, “we need to stop doing this” or “we need to do this differently”.
Those “do” and “doing” are the key, whatever “this” is.
It’s the behaviour our software exhibits that is most important, almost everything else is secondary.