Brush Hard. 

About a month ago I figured out that people don't squirt the toothpaste in their mouth and then brush their teeth. Genuinely thought that everyone who put it on the toothbrush was out to make me look the fool and it was this big running joke to make me seem strange. I still do it though. burnoutbonfire

Undie Check....

Goes through their underwear periodically, and culls out the ones that need to be thrown out. Jcampbell1796

I have to do this with my husband's underwear, because he wears them until they're practically just a waistband. pinkkittenfur

Buzzz...

instead of being on a phone, I use the time on the toilet to shave my head and beard with an electric razor. Wrong_Answer_Willie

Facts. 

When i was 14/15 I thought it was normal for everyone to feel suicidal on a fairly regular basis. Turns out it's not! Took about ten years to finally resolve all that but life is so much better now. Mermaidfishbitch

I was on a school trip, and I mentioned suicidal thoughts as a regular fact of life. My friends were all horrified. I genuinely was in the same boat as you, had no idea it wasn't normal! Ulmpire

Calm Down a Little....

I grew up in a very conservative community. I pretty much grew up believing that much anyone on the internet that I don't personally know must be from ISIS, wants to kill me, wants to kidnap me, etc etc. This naturally resulted in never talking to anyone I didn't know online.

Turns out, most people on the internet are (believe it or not) just average people. Obviously, there are sketchy people here and there, but not anywhere near the amount I thought there were. Transparent-Paint

I could see!

I started losing my vision when I was in early elementary school, and by the end of fourth grade it was so bad I couldn't see my hand in front of my face. Since then anything farther away than arms-length distance is blurred out of existence without visual aid.

When I was a kid I thought the world looked that way to everyone so I never said anything about the fact that I couldn't see shit. My teacher, thankfully, noticed I was struggling to see the board and running into stuff and informed my parents.

They had my eyes tested, and then when I was given my first pair of glasses I realized what I was actually missing. I remember being told to look at this tree far, far away, all the way across the parking lot of the optometrist's office, and describe what it was like. I remember being shocked by the vivid color and every individual leaf - I could see! Reddit

Oh Grandpa. 

So growing up My Grandfather had an airplane hangar where we stored a lot of our stuff. It took me until I got to college to realize not everyone's grandpa has an airplane hangar. Mr_SYG33

 "self directed speech"

Talk to oneself. I thought everyone talks to themselves. Turns out not many people does and if you do it when people are around then you'll be ridiculed. SiddharthKothari93

This is actually a normal thing. It's called "self directed speech" and is easily observed and encouraged in children. The purpose is usually to coach yourself through a certain unfamiliar situation and guide your thoughts and actions to make the appropriate choice/action. RomanticAnarchy

With a Spoon.

Eating marmite plain, like with a spoon.

i have been to Australia and eaten vegimite, its milder in taste and a bit less salty, but bovrill, ugh i keep a pot near my bed cuz its just so damn good. willcanton

The Snow. 

Seeing "pixel"-like shapes when it gets darker. I couldn't figure out how my bf would see in the dark with all those "pixels" and he was like"what are you even talking about?".

Apparently it's called visual snow and not everyone sees them haha. shame95

So that's what it's called! I tried explaining it to my parents once as static tv vision! peachlanz

Obviously, I was the only person to do it.

My mom always taught me to put folded up pieces of toilet paper between my butt cheeks, to absorb moisture and make it comfortable. Like 12-16 squares folded up, and just sort of tucked in there. It seemed logical.

I made the JV football team in my sophomore year, and after the first practice, I was immediately ridiculed in the locker room when I took out my butt-paper. Obviously, I was the only person to do it.

The razzing continued for the year, but I never did it again. Captain_Hampockets

Past 6:30....

That everyone went to sleep at 6:30pm in the summer. My parents were very strict about bed times throughout my youth. I only realized it wasn't true when the AC went out and we had all the windows open. I could hear kids playing and hear the ice cream truck.

ADDITIONALLY:

Until high school graduation when I had a curfew it did not mean be home by. It meant home and in bed asleep. No movies/books/tv. fourtaco

The Fuzz....

Up until I got glasses in 4th grade I thought car lights/street lights looked like fuzzy shiny stars to everyone. roylitchi

I've been driving for 5 years, I never thought about this and now I'm scheduling to get my eyes looked at so thanks. taylorerowland

"WTF IS SNACKING BUTTER!?"

My mom always let me cut up little bits of butter to snack on while cooking. I explained to my friend recently (we are now in our 30s) that I buy cheap butter to go into the food and expensive butter as my snacking butter. The look on his face when he said "WTF IS SNACKING BUTTER!?" lmao I guess I'm the only one

EDIT:wow I didn't expect this to blow up like this, but let me say one thing to everyone warning me of an early grave: consider what you're saying.

If I told you I occasionally enjoy a slice of toast with butter on it, you wouldn't bat an eye. When I tell you I occasionally enjoy a small cube of butter, I'm on my way to death of clogged arteries. You sound stupid af. hail_to_the_beef

​Being really tired all the time.

Being really tired all the time. Everyone always says they're tired all the time so I kind of just resigned myself to the idea that I was supposed to always be stuck right on the verge of sleep. Turns out I have narcolepsy. pots-and-pans-robot

All Seeing...

My 5th grade band director asked me one day why I was consistently almost spot-on when tuning at the top of the class. 5th grade was the first grade where band was offered, so basically all the other kids were way off pitch except for me. Naturally, I reply with "Oh. I just memorized the color it makes and match it every time!"

Turns out, I have Synesthesia, specifically Chromesthesia, which means I can see sound. FishtopherGoblin

yada yada yada.....

Freshman year of college bunch of guys ripping on each other joking around. This one guy says yada yada yada "I bet you don't even masturbate on your knees."... As an insult... The guy seriously thought that the only way people masturbate is kneeling, and was shocked when no one backed him up. Needless to say he never lived that down. Tato7069

The Sound of Silence......

A few years back I said to someone "I wonder what pure silence sounds like" and they were really confused about what I meant. After trying to clarify further they said, dude I think you have tinnitus... So I realized in that moment I have had it my entire life...

I always thought our ears weren't capable of picking up complete silence so we always had some sound coming through (ringing) when no other noise was present. I just assumed for 20 years everyone heard that noise when it's silent and never brought it up until then.

Also explained why I've had a hard time sleeping when it's completely quiet my entire life. Sleep so much better with enough sounds to drown it out. Quzga

Mixed Up 101...

That everyone mixes up words and has a hard time reading numbers and sentences. Finally had a professor pulled me aside in my Accounting 101 class and asked me if I had dyslexia, that I realized it is indeed not normal. Especially to this severity. No, its not normal to have to reread the same sentence or number 5x before it shows up correctly. Math sucks because you often are not sure what the number should ACTUALLY be. BioshockBombshell

+/-

I thought everyone just thought about me negatively and talked about me when I wasn't there.

Turns out nobody cares and people are busy worrying about their own things and don't have time for that stuff. BandNerd_