For instance, one thing I learned in my dating that I couldn't perceive before hand: I want a partner who's more open, and more honest, and holds back less.
It is pretty typical for both men and women to refrain from holding back their opinions or talk about what's bothering them-- being worried about offending or hurting the other party, or just chicken to rock the boat. Of course, this has varying severity in each culture (with it being much less of an issue between Americans compared to Japanese, and simply non-existent when dealing with very blunt Chinese people), but people also have varying tolerance for candidness as well.
There's a reason why we all learn manners and learn not to offend people; and many partnerships, romantic and otherwise, just work better when there ISN'T 100% relay of all personal information (not due to dishonesty, but due to tactfulness).
As I said, people have different comfort zones of "too much" and "too little"; take me, "more in better" in most cases-- and I would be annoyed as hell to date a mouse of a woman always keeping her complaints inside. That said, some blunt Chinese women I've met ("Wow, I thought you had a nice body until you took your shirt off!") wouldn't have been a good match either...
This is just an example of one self-aspect that's hard to discern in yourself without experience, and EVEN HARDER to discern in your partner until you've dated them more thoroughly.
There are definitely people who make it work with less experience. For instance Japanese, while less open and honest communication compared to Americans, also have strongly ingrained culture that makes people more like-minded from the onset (ie. less need for open communication, higher chance of compatibility without much get-to-know-you). Highschool/middle school Japanese relationships usually take a minimum of 3 years and last a life time with a much higher rate compared to Americans. That said, pull up the birth rate numbers and you'll see their method isn't exactly successful either.
Then you look back at the American divorce rate numbers. lol