Confessions of a researchaholic

Students take courses in college, and do research in graduate school.

Taking courses and doing research share some common intellectual underpinnings. On the other hand, they are also very different. Different enough to make some college superstars completely fail in graduate schools.

When you take a course, everything is pre-designed and deterministic. You follow the instructions. And if you are smart and hardworking enough, you get good grades.

When you conduct a research project, very little is known a priori. The process is ambiguous and stochastic; your assumption may be wrong, your experiments may fail, sometimes you might not know what you are doing, and in the end your papers may get rejected. Being smart and hardworking can help. But if you have to follow clear instructions and you expect deterministic outcomes, you probably will not enjoy or be very good at research.

This is probably why, in my personal experience, the best research students might not have the best GPA, but they are usually creative, motivated, tough, and (most importantly) can get things done no matter what happens.
(Perfect GPA can be a reflection of conforming personality, which is not suitable for research. On the other hand, bad GPA is usually a reflection of intellectual or personality problems.)

The transition from undergrad to grad school is not always easy for everyone. My suggestion is to adopt the research mentality as early as possible. In particular, do not waste your time on courses; all you need is to pass the minimal requirements. If you have to, take courses that are research or project oriented. And start your research as early as possible, so that you will have more time to learn and adjust, and to accommodate all the potential failures and setbacks.