Ah...the "big year"! I've had many people come to me about this. Honestly, the best way to get through the year is time management. Do whatever is necessary in terms of your workloads. If your teachers provide you with calendars, be sure to check them. (For example: If you check your schedules and see that you have 2 tests or more in a week, plan ahead. Make plans with your friends for after the tests. Or even better, get together to study with a couple of classmates instead!) Another way to help yourself focus is to eliminate any distractions. (For some people, this may mean turning off notifications for Snapchat, Instagram, Facebook etc. Or even charging up your phone in a room separate from where you will be studying. For me, I did a combination of both...and still do sometimes.) Self-discipline at this stage is very important to develop, because soon enough you'll be off to college! Nobody will be there to follow you around telling you what to do, so it's good to start figuring out now what works for you in terms of productivity, focusing etc.
Additionally, it is important to find the thing you need most to get through a day. This could mean proper rest, snacking, water, meditation, a healthy meal, putting on makeup(or not), breakfast in the morning, a shower... If you feel seriously energy deprived, play around with your schedule and routine until you find what makes you feel better. Personally, I realized that anytime I fall asleep past 2 in the morning on a school night, I will feel terrible the next day. On the other hand, I also realized that whenever I fall asleep before midnight, I feel well rested. Showers and face washing are also crucial parts of my routine. It all varies from person to person!
The last thing I will say about this is don't overthink it! Yes, you are a junior now. You've become an upperclassman. You have probably heard people talk about how important the year is. But don't panic! I remember being so scared when I first entered the year. I actually ended up blooming...I did better in my classes than I ever have and made friends I will keep for a lifetime. Yes, there were stressful moments for sure, but I worked through it in a healthy way. From my experience, the year made me much more mature, pressure proof and actually happier as a person. I believe the same thing can happen for you. Turn that frown upside down, because you are taking steps toward true self-discovery and freedom!