What's an adult problem nobody prepared you for?

that nobody grew up, but i was supposed to pretend the adults around me were anything more than tall children.
- Right? Why did nobody tell me that being adult just meant everybody around you essentially larps as an adult?
  Also as a child you assume that adults automatically have their shit together and then at some point you realise that almost no one has.
  
  yeah. i know it's hard to "prepare someone for the real world", but letting a kid or teenager know that none of the adults know what they're doing and aren't acting according to any set of rigid rules might break through that shell.
  "People will be more mature in high school/university/the real world" is some misleading bunk.

How much you have to wing it. I thought adults had shit figured out, but it turns out we're all making it up as we go along.
In homes the kitchen is never properly clean, it always needs something doing. And if you're a home owner there's always something that requires maintenance!
- Thanks for reminding me my toilet roll holder needs tightening. That's critical infrastructure.
  
  Ugh your comment just reminded me I need to mop the bathroom floor

Chronic pain.
Technically children can have chronic pain, but it gets more likely as you get older. There really isn't anything to do about it, and no way to prepare for it, so no-one really talks about it.

That most of those homeless people are elderly and disabled; that there is no real social safety net and we're all supposed to just die if we get hurt. If all the homeless were gassed no one would ask questions or care in the USA

Light-hearted: Taxes lol
Reality: caring for your aging parents. And burying them

Knee problems
- Ugh that's hard, people don't realise it's not just a hinge it's far more complicated

The sometimes maddening weight of providing for my family.

Death of a parent and managing their assets.
Just never talked about sickness and death. You always assumed they would be around.
Some cultures and religion make end-of-life stuff really difficult on the kids.

Nobody ever told me that if you don’t want what other people have, then you probably shouldn’t be doing what they do and expecting a different outcome.

I was told that being cheeky wouldn't get you far, cutting in line was wrong, being nice to people would make life easier. Turns out being selfish is pretty much the best way to survive.
- On the flip side of this, i think its okay to be that way, but we should also try to do what we feel is the right thing to do. What surprised me about being an adult is how incredibly unique everyone is, and how much crap we all go through. It can be a problem at times, but its also great to step in their shoes and learn a new perspective.
  Going into any social situations, I try to be aware that someone may be having a rough day, and a small, unexpected, friendly gesture can help make their day a bit better. Even if it takes 5 minutes out of your entire day being inconvenienced (thats 0.35% of your entire day), you can make someones day 100% better for the rest of their day, week, or even month. It just feels so rewarding to help when you can. At least it does to me.
  
  Just an anecdote of something that happened mere minutes ago: I was at the supermarket and we have this plastic bottle recycling system where you pay for the package and you get it back once you hand in the bottle at the supermarket. You'll receive a kind of coupon with a bar code.
  Some older dude before me handed in some bottles and got out of the way quickly because I was in line behind him. I noticed that he forgot his coupon but he walked off rather quickly. He stopped pretty close to the machine so I handed in my three bottles and took his coupon and my own. I then sought him out and gave him his coupon.
  It was just a very simple thing for me, it was his ticket, I knew it was his and I could find him easily so giving him his coupon was a no-brainer. It was only for 75 cents but that doesn't really matter.
  He was very surprised and happy with my action.
  It got me thinking. What would the situation have called for in order for me to behave differently. Would I not have returned his wallet packed with cash if he'd dropped it? No. So the amount of money is not the issue. Would I not have sought him out if he had moved further away from the collection machine? Maybe. I would've taken the ticket and moved around a bit to see if I could find him. Would I not have gone through the trouble if it was anyone other than an older gentleman? Not really.
  So in short: you can always do the right thing in these situations, no matter if the parameters are slightly different.

Nobody told me that friendships stop existing after a certain point.

Life

Clearing clogged milk ducts while exclusively pumping for my baby. The most painful experience after delivery if not emptied.
- Yep it's one of the 4433543 things about pregnancy nobody warns you about

How common sleep injuries are going to become

Taxes

University