Maxing out on push-ups every couple of days is good fitness advice, but using them as a proxy for general fitness is problematic: it's very easy to exchange form for higher repetitions when doing push-ups, especially if you're not working with a trainer or gym buddy. There's a built-in incentive to do this if you're using them to measure your fitness, and it's easy to do it unconsciously. Falling into this trap gives you a false indication of progress, and also limits the quality of the exercise: you need a full range of motion to engage all the muscle groups involved.
The only way to keep yourself from doing so is to consciously prioritize form: your back should be straight, your body should just brush the floor at the bottom of its motion (chest and groin more or less simultaneously), and you should straighten your arms as far as they'll go without locking your elbows at the top. End the set once you can no longer do this.
I am beginning to suspect that it is surprisingly common for intelligent, competent adults to somehow make it through the world for a few decades while missing some ordinary skill, like mailing a physical letter, folding a fitted sheet, depositing a check, or reading a bus schedule. Since these tasks are often presented atomically - or, worse, embedded implicitly into other instructions - and it is often possible to get around the need for them, this ignorance is not self-correcting. One can Google "how to deposit a check" and similar phrases, but the sorts of instructions that crop up are often misleading, rely on entangled and potentially similarly-deficient knowledge to be understandable, or are not so much instructions as they are tips and tricks and warnings for people who already know the basic procedure. Asking other people is more effective because they can respond to requests for clarification (and physically pointing at stuff is useful too), but embarrassing, since lacking these skills as an adult is stigmatized. (They are rarely even considered skills by people who have had them for a while.)
This seems like a bad situation. And - if I am correct and gaps like these are common - then it is something of a collective action problem to handle gap-filling without undue social drama. Supposedly, we're good at collective action problems, us rationalists, right? So I propose a thread for the purpose here, with the stipulation that all replies to gap announcements are to be constructive attempts at conveying the relevant procedural knowledge. No asking "how did you manage to be X years old without knowing that?" - if the gap-haver wishes to volunteer the information, that is fine, but asking is to be considered poor form.
(And yes, I have one. It's this: how in the world do people go about the supposedly atomic action of investing in the stock market? Here I am, sitting at my computer, and suppose I want a share of Apple - there isn't a button that says "Buy Our Stock" on their website. There goes my one idea. Where do I go and what do I do there?)