If it aint broke dont cut it off to spite your chickens before they've hatched

Yes it's a mix of euphemisms. Beware of euphemisms, they are quite often wrong.

One I've heard a lot is "doing the same thing over and over and expecting a different result is a definition of madness"

This euphemism fails dismally as a rule that can be applied generally, it should actually say, "If all conditions or actions other than the one you are performing, that can influence the result, have not changed, then its reasonable to assume you will get the same result if you perform the same action in exactly the same way". This covers scenarios like starting the lawnmower the seventh time you try or investing in gold one year and making a huge profit or investing in a different year and making a huge loss.

Even if circumstances are exactly the same, its still a dubious assertion, after all we are human beings and as is evidenced by my inability to be consistently good at pool, we never do things exactly the same way even twice.

So next time someone trots out some euphemism to justify their world view, think about how reliable it is. It may not be worth the brain cells it's written on, or you can "go with the flow" or "let sleeping dogs lie" or ... well, you get the idea.