There is this saying "Every rule has an exception!"
Further, as an exception to this rule, there must be some rule without exception.
So we know there are exception to this rule.

Now, how an exception gets decided:

1. Somebody succeeding in something without following a required rule is called an exception.

2. Somebody failing in something because not following a rule is called a proof of the rule.

So, the understanding is that there is just one rule. Make sure you succeed in whatever you are doing.

The moral of the story is "Nothing succeeds like success!".