Falling or tripping over in public is not in itself embarrassing; it happens to everyone and you can always laugh about it with your friends or whoever else you’re with (and it’s good fun for them cos they get to go “wahay!! yeah!!” which is always fun).
What is embarrassing is the moment after you trip over by yourself. It’s funny for people who see you because they’re laughing at how much of a loser you are and your complete ineptitude to even walk in a straight line. They’re laughing at you because you are a joke. So whilst you think that by breaking out into a grin you’re making yourself look cool and breezy like you couldn’t care less… what’s really happening is that you’re effectively laughing at your own joke whilst also admitting that you’re a cripple unable to perform even the most simple tasks. aka a fucking a loser.
Anyway, one thing I’d definitely recommend you don’t do to shirk any potential embarrassment is act like this guy… When I saw him stack it down the stairs in a pub in Camden I (of course) immediately took a photo. When he finally made it to the bottom he came over to me and said “most guys would help a brother out. But you took a photo. I hope you burn in hell”. Hahahahahahahahaa. Sorry bud, someone taking life maybe a little too seriously these days?? Admit it, you’re such a fuck up that you can’t even walk down a set of stairs without fucking up! hahahahahahahahah