I didn't do pre-IB, but i am now about to finish my first year of the IB and i got through it just fine. I think what's really important is that you actually work everyday and that you remember that having a social life is important too. For example, i hace made a point of never studying on fridays, that's the day in which i can actually relax. Also, GET SLEEP! A lot of people will tell you that IB kids never get any sleep, but i've slept eight hours per day since the school year began and i think that has helped a lot. Good luck, anyways!