It sounds obvious because it is, and it works. Keep track of all that you need to do, and write it all down. It's also a good idea to track all of your commitments on a single calender -- that way you can avoid double-booking your time. Keeping track of your engagements will also make it easier to say no to friends who want to party the night before a big test. It's much easier to point to your schedule and say you have a real and present reason for staying home, as opposed to an excuse like "I just don't feel like going out tonight."
No matter how strong your resolve, it always helps to keep friends that are good influences and who are supportive of your desire for balance in college life. Not that a few more impulsive individuals won't help keep things interesting; try and maintain a core of friends who view the need for grounding and balance similar to the ways that you do. They will serve as a constant reminder of your own goals, and you will provide the same for them.
Earning money while in college is important, especially if you are paying for your education yourself, but try not to let it control your life. Look for an employer who understands your position as a student and will be flexible either with scheduling or commitment expectations. Even if your current job pays really well, if it takes up too much of your time it might be advantageous to find a new job that better accommodates your multifaceted lifestyle.
Over the course of your college education the stress will mount, and not only with academics. Work and play will also weigh upon you, and you'll need to find an outlet for your stress in order to manage it. For some, the establishment of daily routines is enough, such as stopping for coffee after work each day. Others exercise or nap or utilize local support groups or the free mental health services offered by most schools. Whichever outlet you choose, keep it on your calender; it's just as important as the other elements in your life.
Finally, in light of everything else on your proverbial plate: the tests, the work, the tracking of your obligations, the social life; sometimes you'll need to just slow down, step back and see things from a larger perspective. You're in college. Ultimately, it is a few short years of your life. You will have successes and you will make mistakes. Try and remember that this is a time for you to grow and change in all areas of your life, and you owe it to yourself to try and enjoy and treasure it as much as possible.