Hahah, I remember my mom saying that my teenage sister needed "to learn she can't always get what she wants" in the most condescending voice possible. I was like, "Really, Mom? What's going to happen if she doesn't ever learn that? She might accidentally go through life getting what she wants i.e. being successful?" Of course she couldn't give me a good answer. She had only said that because she wanted to be vindictive. (Partially because my sister is a brat, and partially because my mom is the sort of person who can't ever decline requests politely, i.e. if a family member wants something, Mom either has to provide it or has to villanize the family member.) I feel that the idea that kids need to be forced to learn all those vague negative lessons about the "real world" (from school) came from adults who are all bitter and jealous over the idea that that kids might have the audacity to go around being happy.
If anything, I think school is more likely to teach distorted versions of those lessons, and we just have to hope the student overcomes it later on. Think back to the last time you did boring stuff. Was it because some authority figure told you to, and you had to worry about your parents inflicting some punishment on you for not obeying? Or was it because you considered your options and decided that was the best course of action for getting what you wanted? Hopefully the latter. That's how I'd prefer my kids to go about their adults lives, but from my experience, school isn't really supportive of that mentality.
Plus, I totally have that "the world and life is not as cool as they thought" problem. In my case, I feel it was actually a result of being conventionally schooled. I didn't get to have much say in my education, and looking back, I realize that I put a lot more effort into school than I think was wise. (And to think that I had it so much better than so many others! I was academically talented and was able to get good grades with less effort.) I did it because my parents and others essentially told me things that amounted to, "Put everything about your life that makes you happy on the back burner for 13 years [plus college] and focus on this other boring tedious stuff instead. If you do this, you will then be able to get a fun and exciting job, that pays lots of money for you to use to buy fun and exciting things and experiences! But if you don't do this, you will have a physically painful, boring, low-paying job! I mean, look at [insert pathetic extended family member]." So I trusted them, got good grades, when in debt to go to college, got good grades again, and... I have a physically painful, boring, low-paying job! With zero benefits and zero job security! I can't pay my own bills, and I've almost been fired because I'm not even very good at the one job that'll hire someone with as few job skills as me. So, yeah, I feel a little betrayed. I sacrificed 13 years of my life for this? That's why I'm so drawn to unschooling (and democratic schools and relaxed homeschooling to a lesser extent): I figure there's no sure-fire way to make sure your kids are prepared to obtain whatever careers will make them happy, so you might as well at least let them enjoy their childhood.