Need serious advice with undergrad physics

[JVanUW]

So this past spring as a freshman I took intro EM, intermediate mechanics (lagrangians etc), and one-semester quantum mechanics using griffiths. I got an A in quantum (which freshman never take) but unfortunately I slipped up in my other two classes and got AB's (slipped up is verbatim from my advisor). Next year I have the option of doing graduate quantum mechanics using sakurai, and the professor says she thinks I can handle it.

This is my question. After letting two classes that I should've gotten A's in fall to the wayside (one of them was an intro class), I feel like my acceptance chances at my dream university Princeton have been diminished (I have personal reasons for wanting to go to Princeton, not just because it's quite reputable for physics). Could taking graduate quantum mechanics and excelling drastically make up for my previous semester? Do students take graduate classes as sophomores? Would I be better off investing this time in research?

Thanks for your advice!

 

[PhizKid]

Sorry for not answering your questions but I'd like to ask you: how did you slip up? What did you do wrong? What should've you done in order to get the 'A's in those classes you didn't?

 

[JVanUW]

I had an lazy off-weekend that happened to be the weekend I had a take-home midterm for mechanics, and I ended up a standard deviation below the mean. For E+M I had trouble sleeping the night before exams and I legit got 3 hours of sleep before two of them.