Having sex can cause pregnancy. This one seems too obvious to mention, but judging from the number of "oh, shit, I'm pregnant" pregnancies in the world, I thought it bore repeating. Nothing is 100% effective against pregnancy except abstinence, or the removal of your ovaries or testicles.
If you cover your body with piercings and/or tattoos, you may not be able to find a job. This also goes for doing weird things to your hair. And please don't give me any bullshit about "freedom of expression". You go right ahead and express yourself all you want, but don't expect businesses to be under some kind of obligation to hire you. They can't not hire you for being a Jew, but they certainly can not hire you for looking like a fucking freak. (caveat: I have tattoos … And I have nothing against tattoos, piercings or fucking freaks. Just don't whine about it when you're treated like one.)
Marijuana is not a "gateway drug". OK, maybe 99% of "hard" drug users also smoke pot. And maybe a lot of them smoked pot before they got into whatever hard drug it is that they're using. But that's not because the pot made them do it, it's because damn near everyone has smoked pot at some point in their lives.
You have no right to be proud, unless you did it yourself. That goes for anything from racial pride to gender pride to national pride. Your race, gender and nationality are accidents of birth. Being proud of something you got stuck with when momma squeezed you out is assinine. You have a right to be proud of your own personal accomplishments, and perhaps those of your children (if you were actually a decent parent, and your kids didn't succeed by sheer force of will alone). That's it. Your parents had sex, Mom got knocked up, and nine months later, there you were. Race, gender and nationality handed to you out of the accident of your birth. Fuck your white pride, your black pride, your national pride, and all the other bullshit that goes along with it.