I will probably have some disagree with me, & that's ok, everyone needs to adress his own needs! I feel the .38/ .380 are the smallest a person should carry. Most S&W J frames & Colt D frames will fit into the front pocket of most pants. Using a pocket holster will almost always prevent "printing". I know the .32s are gaining in popularity, & the .32 mag & .327s are popular. These might work as well as a .38? I prefer a bit more bullet weight. This said if all I had with me were a .22, I'd use it if I had to. In fact the Beretta 21A is a very concealable gun & more accurate than most would believe. Still I'd rather have a .38. Whatever is used become proficient with it, able to hit a 8" target in a big hurry at 3 & 7 yards. Bullet placement is king, power is secondary. It's probably been said before, but I first heard it from Bill Jordan, "speed's fine, accuracy is final" Seem applicable today too.
Mindset isn't talked about as much as it should be, develop the mindset that "I'm going home no matter what happens, I win" be smart, use cover, & probably the most important "be aware of what is around you" Avoid dangerous encounters if at all possible. The macho mindset has no place in avoiding confrontations. Since I retired I have the option to run if need be, does someone see this as cowardly? Maybe, but it may keep me from having to kill someone & surely keep me out of court. Be smart, don't develop an attitude because we are armed. Friends who go armed every day have become the most polite people I know!
Thanks, Frank