Most students struggle with time management, and therefore, health. Your body and brain need sleep. You cannot sleep if you do not manage your assignments and projects effectively. If you are sleep deprived, you are more likely to get sick and require time off. I encourage you to make a working schedule and stick to it, and if you are up for it, to make time to exercise in whatever way works for you.
Mental health is also often adversely affected during graduate school. With pressures so high and deadlines so short, students often abuse substances or fall into unhealthy habits. I encourage you to find and use any resources your school provides for maintaining mental and physical health.
Last, many students struggle with the job search at the end of graduate school. I encourage you to start making connections and going to networking events like it is part of your job (because it is). You never know which connection could turn into employment. You cannot always rely on your resume to get your foot in the door, so use whatever resources are available and get every advantage you can. Start looking for internships or employment a full year in advance. Other students or even the school itself may discourage you from starting so early, but you stand to benefit from your efforts... and they do not.
Good luck in graduate school! It changed my life for the better, and I hope it does for you, too.