Visitor Visa - B2

Yesterday, I applied for B2 visa to the US. Im 22. I live in Poland. Ive been working as secretary in kindergarten from Feb 2013. I quit studies.
I really want to visit my friend in L.A. We've got common interests in music. There will be NAMM show in 3 weeks, ive been dreaming to attend for years, and he helped me to get pass for this. Until yesterday, I was convinced visa was an only formality, but i got denied...

Me: Good Morning
C: Good Morning
C: Why do you want to go to the states?
me: to visit my friend
c: how did you meet him?
me: in may, in barcelona
c: how old is he?
me: 54
c: what is his job?
me: music producer
(he was smiling to me for all this time)
c: who do you live with?
me: parents.
c: how long youve been working and what is your job?
me: secretary in kindergarten, since Feb 2013
c: did you study?
me: yes, i quit, but im gonna start studies again soon
c: what did you study?
me: psychology, for year
c: where?
me: krakow
c: unfortunately, your career doesnt satisfy me. get back when you have husband, kids, or have good career. bye.
me: please...i just want to go there for 10 days...its a trip, i dream about it...
c: bye.

There is no much time left. Im ready to apply again this week... my friend wrote a special letter telling them he is going to take care of everything. I have contract of employment.Im ready to enroll for studies.
What do you think, what would you do if you were in my shoes? Any suggestions? Maybe there are some other documents i should bring? I ask for your help...
thanks in advance