Let's use pirates as an example. Why pirates? Because pirates are fucking cool. That, and they don't live up to their name either. Let me explain.
I've had this craze with pirates as of late. It started with this Wizkids pirate game they stopped making a few years back. Then came Alestorm, the (awesome) pirate metal band. (Check them out at www.alestorm.net.) After that, I rewatched all four of the Pirates of the Caribbean movies. Which, by the way, are excellent movies. Finally, I began to recall and toy with Captain Viktor and his pirate crew, who are my main characters in a collab project I'm currently working on with my friend Amelia Lynn. So, I did some research (out of pure curiosity, mind you) and very quickly I began to realize that Disney's freedom-fighter pirates only vaguely resembled actual, historical pirates.
Normally, the captain of a pirate ship was elected by the popular vote of the crew; and they reserved the right to strip his position from him should he abuse his power or slack off. Quartermasters were actually what we imagine as first mates; managing the crew, keeping them in line, and rationing out supplies. First mates actually took the place of a sort of "second captain." (In Disney's defense, they kind of fixed this in the fourth movie with Angelica.) Moving on; an average of half of all seamen (not just pirates) died of diseases like scurvy, dysentery, tuberculosis, and smallpox. These were brought on by the poor living conditions at sea; the constant closeness of the always filth-covered, soaking wet crew; and the never-ending work and exhaustion onboard.
Quite often, pirates gathered crew by attacking ships and forcing able-bodied sailors into service (usually under threat of death), especially if they were especially skilled in a certain profession (such as carpenters, surgeons, and chefs). Women were not just considered bad luck at sea, they were not permitted aboard ships of any kind. (There were only ever two female pirates.) Besides the obvious "bad luck" that they brought with them, women weren't as capable at sea as men were, they were more likely to get sick, and bringing one aboard would usually mean slowed progress. Scallywags, thieves, and cutthroats, the lot. Pirates were not organized renegades fighting the governing countries (though they technically did rebel against the political powers of the time) with a pirate council and a king, they were ruthless plunderers who attacked ships and stole goods, coin, crew, and anything else they needed or wanted. A far cry from the good-natured Captain Jack Sparrow, eh?
All of this, I suppose, to say: not everything (or everyone) will live up to expectations. And not everyone is exactly as they appear to be. Everyone wears masks. No matter why (be it fear to reveal their true self, societal pressure to be someone else, or having to wear the mask for so long it becomes normal), there is something beneath that mask that (most likely) will not match your expectations. Because people don't just wear masks for the fun of it. It isn't fun. It sucks. There is always a reason, and your expectations are likely a part of it.
Remember that the next time you talk to someone. No matter how long you've know them. Realize that there is more than likely something lurking behind a mask that doesn't meet up with what you expect. It may take a little work, but if you can accept that not everything will be what you expect, you'll find exactly who they are. And it works the other way too. Drop your mask(s), because you can't meet everyone's expectations. You might as well be the real you.