Ah yes, my favorite time of semester: the week all of your design projects are due.
Unless you are some kind of magical design wizard, there will likely be times in your school career where you need to make a decision on what projects are most important, and what ones you may need to sacrifice a little time on. While it's a tough decision to consciously choose to spend less time on a project than you would like, it's important to keep in mind that your ultimate goal should be to continually improve your portfolio work. One subpar project isn't going to effect you in the long run. Everything is a work in progress- it's extremely likely that even the project that you are most proud of can still be improved greatly. Take some time away from it and come back- you'll see a ton of areas in which it can be improved. If you run out of time on a project, think about what you can do to get the best grade possible and take notes on what you would like to come back to and improve later - though it's best to keep improving while the project is fresh in your head.
I'm no stranger to picking and choosing my design battles, though when the clock is counting down, I do a few things to help me get as much done as possible.
1) Prioritize - I use the iPhone app Clear to keep track of what I need to get done in order. If I change my mind or something comes up, it's easy for me to reshuffle or add new priorities.
2) Set Deadlines - If you are really down to the wire with multiple projects, tell yourself you will spend no longer than 'X' minutes or hours iterating on a concept. It's easy to get sucked into a black hole of designing and redesigning a small aspect while often only improving it marginally. If I find that happening when I'm crunched for time, I set a timer on my phone and tell myself that I will be done with it when the time runs out. Often times the pressure for the timer actually helps me create something I'm satisfied with.
3) Stay Healthy and Hydrated - This one is super important. If you are pulling a few nights with little to no sleep while downing a bunch of coffee and energy drinks, offset it with some healthy snacks and a lot of water! You'll ultimately crash a lot sooner if you become dehydrated from all of the caffeine and salty snacks you are consuming - I've learned this the hard way!
Well, I need to get back to it. 24 more hours to get everything done! Good Luck with your final projects!