It's pretty common for people to do worse in pre-calc than in calc. Pre-calc introduces you to a lot of topics, some of them pushing you away from comfortable areas. Examples of this include polar coordinates (away from good ol' x-y coordinates), analytic geometry (away from "visualizing" graphs), and conics (...both...). Calc, on the other hand, can be straightforward or extremely rigorous, depending on how it's taught. If all you're going to do are basic derivatives and integrals, then it shouldn't be a problem. But if you have to prove every theorem you use, then you're really in for it.