In a post on JohnK’s blog where he was explaining the problems in “Canadian-style” animation, he said:
TOO MANY ANTICIPATIONS Every pose is connected with the next by an anticipation and overshoot. Every single one! No one ever just moves from one pose to the next easily. There is no variance in timing or posing.
This struck me, along with another post where he tells a story of a background artist who used the “Rule of 3” because “even numbers are symmetrical, odd numbers are more interesting.”
Both are examples where I can sort of see why someone would be attracted to these rules, but then they let those rules sabotage themselves by thinking, “If I follow this rule all the time without exception, then that will be the best animation possible.”
So the lesson is, I think, any time you think you’ve found a rule that will help you make great art (of any kind, not just animation) then you should immediately start thinking of the exceptions and variations on that rule. If you can’t think of any, you don’t really understand the rule.