Here are some suggestions for maintaining your health during the new school year:
1) Have a healthy study schedule. You will learn much more efficiently and enjoyably if you study regularly, in a disciplined schedule. I don't believe it is possible to master any subject, much less build up an enjoyment of it, by procrastinating or cramming. Each full-year course probably deserves about 200 hours of study, to be spread out as evenly as possible. Mastery of a specific field of study probably requires about 10 000 hours of work, which would be full-time for 5 years. Even if you can get good grades without working hard, I would emphasize to you that doing the bare minimum is an extremely harmful habit--the consequence is that your potential will remain unrealized, also your enjoyment and respect for your subject will never be fully developed.
2) Have a healthy leisure schedule. Time must be reserved for pleasure (outside of the hoped-for intrinsic pleasure of studying or working). A type of "meta-subject" at university is learning to have a pleasurable and healthy lifestyle, with a sense of friendship and community, in the midst of working hard.
3) Be physically active. Exercise & sports will help you maintain your strength, sharpen your mind, relieve stress, and offer potential sources of community & friendship. A common problem, however, is excessive exercise, which drains time and energy away from other activities, and which can cause an addictive pattern leading to a psychological dependence on fitness activities alongside a diminished capacity to manage stress in other ways.
4) Don't binge drink. There is an illusion that binge drinking is an essential part of university social culture. While it may be a common phenomenon, I think many people minimize its extremely negative health impact. Anything more than 2 drinks per 24 hours is, from an epidemiologic point of view, harmful to health. For those dealing with anxiety, depression, trouble fitting in, etc., alcohol can lead to an illusory sense of relief or social belonging while insidiously deepening and entrenching the problems.
5) Eat well. It's easy to neglect this one, particularly if you're living on your own for the first time. Basic nutritional advice is not hard to find. Unfortunately, I think that unhealthy food choices are too easy to find on university campuses. I think that university cafeterias should not sell junk food, soft drinks, etc. (I also think such items should be taxed heavily, in the same way that cigarettes are). It's always disappointing to see soft drink companies or fast food restaurants as major food sponsors, with vending machines all over the place, including in hospitals and gyms, etc. Two simple changes for most people would be to increase vegetables in the diet, and to eliminate junk food. Allowing oneself to go hungry, or to be carbohydrate-deprived, is likely to substantially impair academic performance, attention, and mood.
6) Make cultural choices with care. Developing personal culture is very important, and deserves time and energy. I don't think it is healthy to make a particular cultural choice (e.g. "let's go clubbing!") just because everyone else seems to be doing it. I see a lack of personal culture, with an ensuing lack of a sense of meaningful community, to be one of the leading problems driving loneliness and perpetuating depression on university campuses.
7) Seek medical help if you have symptoms. There are treatments and supports to be connected with, which can help address anxiety, mood problems, physical symptoms, etc. It can be better to connect with resources early, rather than wait for things to get worse.
8) Be wary of viral contagion. A single banal respiratory infection could substantially reduce your enjoyment and learning for a week or more at a time. The best preventative strategy is to wash your hands frequently, especially if handling objects which thousands of other people have handled or coughed on. It's important not to go overboard with this--which could be an obsessive-compulsive symptom-- but basic infection control techniques could save you a lot of headache.
9) If you tend to get tired or depressed in the winter months, consider trying a light box. This is an easy, safe physical treatment which can help with seasonal depression. Daylight is diminishing rapidly in September, so this is probably a good time to get out your light box.
10) Nutritional supplements. Women should have ferritin levels checked, and in general should take iron supplements if ferritin is below 50 ug/L. A daily multivitamin/mineral supplement is a good idea, especially if having abundant fruits and vegetables in the daily diet is not happening consistently. Harmless at worst. Extra vitamin D is indicated, I'd suggest 2000 IU extra per day. DHA/EPA supplements could be useful (omega-3 fatty acids, typically from fish oils). I have some references about this in other entries.
11) Addiction inventory. I'd encourage everyone to take an inventory of all addictive or compulsive behaviours, and take steps to stop or moderate them all. Alcohol or drug use are obvious examples, but other activities could include internet use, gambling, exercise, self-injury, phoning or texting, etc. Many habits consume so much time and attention, that there is much less time, energy, or enthusiasm left for other things that may be more deeply important to you.