At Singapore Airport, there is a huge sign above the immigration gates announcing that drug possession carries the death penalty. Every time I pass through I start questioning how sure I am that I don’t have any drugs on me. (I don’t use drugs or live with anyone who does, and packed my bags myself and didn’t leave them out of my sight, which is about >99.99% certainty, though that >0.01% bears a heavy weight.)

The first several times I flew, which wound up being maybe forty total flights by the time I concluded my long-distance relationship in marriage, I would be "randomly selected" for secondary screenings, bag checks, and finger-tip swabs. Every single time. This eventually stopped happening, but the only thing that really changed was I lost a bunch of weight. I don't know what the connection was.

"Must not look suspicious, don't do anything suspicious, you're not suspicious."
Proceed to give the fakest and most strained smile in history to airport security and get pulled aside..... again.

I actually had this my mind thought “did I bring a firearm?” after I saw a sign saying it would be a criminal offense to bring one through security, when I don’t have any firearms at all in my possession.

You mean, "What if I accidentally have a second gun?..."

Congratulations, we've put you on a list.

-- Your FBI Agent

On a serious note, I once saw a video from a security conference of some sort where the presenter explained he flies with firearms in the US because he can (and is actually required) to use real locks on his luggage.

"What if I accidentally forgot to leave the stainless steel cutout with a ruler, can opener, screwdriver, saw, and a couple blade edges on it?"

...nah, I always carry it in my wallet, right next to the ~~firestarter~~ fresnel lens.