You just tripped over your feet and landed awkwardly (and painfully) on the ground. There’s a small pain somewhere on your body (you can’t really tell,because it all happened so fast) that really just bugs the snot out of you. Someone you know starts walking close and (hopefully) appears to come to help you up onto your feet. Instead, you feel another sharp pain (this time on your face) and see yourself parallel to the world. It’s barely audible, but you can hear your “acquaintance” nagging at you for being so clumsy. And, you can’t really help but feel so dumb.
And that’s just how some parents can be. My own (and hopefully quite a few others) aren’t like that (as much), but when it does happen, it can hurt much more than a slap on the face. Of course, you could say “oh, no one would get angry at someone for doing something so small as tripping”. Well, then why would you yell at someone who has made a small mistake like, I don’t know, getting a semi-decent grade on the test, by just taking a break from studying for a huge test the next day, or by just being plain clumsy as well? No doubt when people make mistakes larger than these, it’s reasonable to be a tad bit annoyed. But when things can be easily fixed (like grades *wink wink nudge nudge*), it’s unreasonable to make the person feel worse than they already feel.
Just like tripping, you should help people up and encourage them to keep walking rather than put them in even more pain than they need.