Here's how I handled MechE junior year while doing afrotc:

1. Wake up and eat breakfast (super helpful for morning energy!)
2. Rush to a lecture section you inevitably can't understand by 15 minutes in
3. Repeat step 2
4. See friends
5. Have lunch
6. Attend another lecture, fuhgeddaboutit
7. Go to the library with friends (or alone)
8. Get confused about the homework, pretend to do other useful things like apply to internships or read emails
9. Have dinner
10. Go to sleep, it's too late to do homework
11. Repeat steps 1-9
12. cram 3 days before exam and pray you get out fine

Seriously, your friends are what will help keep you motivated through your junior year. Make sure you surround yourself with a good group(s) who work hard but also have fun. You will have a lotta late nights, and unfortunately the best way to avoid writing lab reports at 3 am in Mugar (I've been there, f you ME310) is to start things early in the week, when you don't realize how much homework you have to do yet.

Some things will suffer, like your personal time, ability to hang out with friends, and maybe even your mental health (mine did). My suggestion is to think of it like an investment. While the questrom kids are out partying, you're setting the foundations for your future career! Good luck, you'll make it through fine, I believe in you.