At 30 I have realized these things which I have been taught or studied/read since I was a kid.
1.Brush your teeth twice a day.No , spending twice the time and toothpaste and twice the vigor on morning doesnt come under the quota.You are just spoling your already spoilt teeth.
2.Write,write, write, my Mom always used to say this in telugu,ratha(I guess pronounced as raata).Esp in work place, keep a written track of your tasks everyday no matter how efficiently you are in your work and no matter how good your relationship is with your manager.
3.If you make a mistake never ever uncessarily bring it up on your own,if asked dont lie if you can't successfully cover it up.
4.Although there are people few dozens of brave people who learn roller skating or snowboarding (wow , looks like these are the only dangerous activities that I can think of right now) late in their lives,dont try to be too adventurous unless you are ready for months and months no activity period in case of an injury.
5.Boy, cofee does do wonders when you are skimping on sleep.
6.If you get into a situation with his mom,the chances of him supporting you is very less (10%, the first year, and its going to go only lower and I leave the figure to you girls.)
7.No matter how enthusiastic you are about getting busy in bed 5 times a day 5 days a week(A guy's ultimate fantasy), its not normal.So go easy and dont get all compatetive with phony self proclaimed sex goddesses.
8.Just because you like the idea of makeup and those peacock colored eye shadows on a model in a mall, doesnt mean you can wear it too.You will look end up looking like a clown without the haha and hoho's and just Ewww....
9.Its really outrageous for normal mom's to have pan cake maker abs.Enjoy the pan cake instead!
10.Fights(husband) with the spouse come and go.Have a blast in the between period.

Have fun !