As a college professor and a former college student, I can share some observations about college life that may perhaps be helpful for you. Please take my words with a grain of salt though, as everyone's experiences and perspectives are unique.
Take care of your physical and mental health: I encourage you to set a goal for yourself that when you graduate from college, you will be physically and emotionally healthier than when you started college. Numerous studies have shown how important it is for us to exercise regularly, eat well and most importantly, sleep well. If you feel stressed, slow down and take a deep breath. Most things in life (e.g. grades, other people's attitudes towards us, etc.) are out of our control. It's better to focus on what is in our control (e.g. our own attitudes, work ethic, etc). Do not hesitate to talk to a counselor if necessary.
Discover your values and improve your work ethic: While it's understandable that you may be concerned about your grades in college, I can confidently say from experience that you will be much better off in the long-run if you use your college days to discover your values and improve your work ethic. If you pick up less desirable values and habits (e.g. taking shortcuts, making excuses, etc.) in college, it can become much harder to get rid of them later in life. Your manager or coworkers will likely be far less accommodating of these traits than your college professors.
Meet people in college: It may not always be easy but whenever you can, try to go outside of your bubble and become friends with people who come from backgrounds that are very different from yourself. This way, you can learn something unexpected about life and expand your horizons. Get to know at least a few of your professors well. You will find that most of your professors really are looking out for you.
Some courses that I encourage everyone to take: I encourage everyone to take as many economics courses as possible, since these courses can help you make more informed decisions about society (e.g. during presidential elections) or in your personal lives. Additionally, I encourage you to find some philosophy, political science and history classes and treat them as practical knowledge, rather than as theory. If possible, learn a foreign language and participate in a study-abroad program in a country where people speak a different language. They can make a difference to your worldview.
College is not all about classes: The college experience is a very unique experience, so don't forget to enjoy yourself, spend time with friends and pursue some non-academic interests (such as volunteering or pursuing a hobby) as well. Pursuing non-academic interests can help you become multi-dimensional and provide a sense of inner fulfillment as well.
Each book below has a different focus; so, taken together, these books can hopefully help you look at yourself and the world around you a little differently.
Peace is Every Step by Thich Nhat Hanh
Siddhartha by Hermann Hesse
Brave New World by Aldous Huxley
Brief Answers to the Big Questions by Stephen Hawking
Why Nations Fail by Daron Acemoglu and James Robinson
A few years ago, I wrote down some suggestions for undergraduate economics majors who may be interested in pursuing a PhD in economics and posted them on Xavier's website. If you have more questions, feel free to talk to me or any of your economics professors.