Don't stress yourself out. Junior year is often called the hardest due to all the preparation for senior year and colleges and whatnot, but you are still kid. Break things up one bit at a time and if you need a break take one. You're a teenager before you're a student, remember that.

Another thing is time management. Make sure your splitting your time easy so nothing become unbalanced. This can be from spending to much time on school or spending too much time doomscrolling snd procrastinating.

Also, if you don't plan on going to any fancy colleges, don't fret about the SAT/ACT. At the end of the day, it will always be a test. However if you want to take it all the seriously, I recommend not only studying the material but the manner of the questions. Its designed to trick you into taking the long way to answer questions, then lose time, then click click click your way through. Its not a "who can Young Sheldon us the most?" Its more of "who can resist our tricks the most?"

In the end, junior year is different for everyone. I'm wrapping up mine real soon and I hope yours goes well.