You don't need to be physically sick to be sick. Mental health is just as important as physical health.
When you're not you, you can't perform your best. Think about it, you're asking a lot from your body. To get to work or class on time, eat, study, get exercise, and sleep if you can. Especially when you're on a strict schedule, it will get to you. People will tell you to push through unless you are physically sick, but doing that will put you at higher risk of catching a virus because your body will become exhausted. I'm not saying to blow things off regularly, but I want you to get in the habit of listening to your body.
Keep the option of modifications in the back of your mind. For example, if you are feeling sleep deprived, one option could be taking a half day. And that could be taking a nice nap in the afternoon, or sleeping in for a few extra hours. Some days, your body could really benefit from waking up at 10 am instead of 6 am one day. The feeling of being fully recharged when you wake up is well worth it. Sometimes it takes a few extra hours out of your day to obtain that feeling, and that's okay.
Ask for extensions. Your professor may or may not grant you one, but it doesn't hurt to ask. If they know you're stressed, they will be more likely to allow it. Communication is key here. They were college students at one point too, they get it. When you're feeling overwhelmed, your quality of work won't be as great as you hoped it would be. Allowing time for self-care can help you get to a better mental state so that you can finish assignments to your best ability.
You don't have to go out every single night on the weekends if you're not feeling up to it. Staying in won't suddenly make you uncool. You are overly stressed, and the weekend is meant for you to unwind and recharge. If going to parties, and bars are going to add to your stress, then give yourself the chance to stay in. Again, when you're having fun you're still asking your body to do a lot. It is okay to say no once in a while. If you absolutely need to, you can dress up for a picture, and then you can snuggle in bed and watch Netflix.
I can't emphasize this enough, mental health is linked to physical health. Any mental illness has its pathophysiology. It's 2017, if you are not in the right frame of mind, allow time for yourself. The mental health field is growing, and it is up to us to continue to facilitate awareness in the media, in our workspaces and campuses. We are the present and future, therefore we are the ones to encourage others to do whatever they need to do to be their best selves.