Given how weirdly dependent this axiom is on an expertise in horse bartering, it's odd that it has stuck around as long as it has. It both presupposes that people are doling out horses as gifts frequently enough that we'd all feel comfortable using that as our context for understanding some bigger truism, and also that we would instinctively know to look for the strengths and weaknesses of a horse by prying open its mouth. Do horses have some sort of natural on-board diagnostics system in their throats? That seems like something Westerns would have covered more often if it were true.
The sentiment, of course, is that you should never be ungrateful for something that's free. It's just a shame that the one example had to be a massive animal that shits where it pleases and can kick a hole through you when it gets nervous.
Great, thank you. I'm sure it will go well in my studio apartment.
In fact, if anyone threatened to give me a horse as a present, I would look for any excuse I could think of not to accept it. And if I knew that I could use some tell in the horse's mouth as an out, that's the very first thing I would do. So really the saying has only taught me a trick to avoid owning a horse, which I don't think was the original intention. That's why, in its place, I submit the much more accessible:
No One Deserves Birthday Cake
While most of us have never tried to force apart the jaws of a horse, everyone has certainly spent a day celebrating their continuing existence by forcing restaurant waitstaff to begrudgingly sing "Happy Birthday" over a free dessert. Birthdays are the epitome of self-entitlement, celebrating a moment in your life that you had absolutely no control over and from which you are already the primary beneficiary. Still, we make special allowances for people on their birthdays, showering them with gifts and parties and Facebook messages, and at the heart of the ritual is always cake.
Now, unless you are 100 years old or the survivor of some debilitating disease, you don't deserve birthday cake. You have never deserved birthday cake. It is something society has collectively decided to offer you as a generous gift to make you feel special. Yet everyone feels entitled to it. We will complain that we don't like butter cream frosting or that the inside is dry because we've forgotten that none of this is merited.
Oh, shut up.