Plan ahead. Set time out for homework. Set time out for relaxing. Set time out for doing both at the same time (studying with friends is tremendously rewarding). Priorotize you assignments: what needs to be done the soonest, what needs the most work, what will I get done the quickest etc, what one is worth more of my grade. and complete them in order of what you think is most important to least important. Make an actual list, not just in your head. Talk to your guidance counselor about how you feel, they see students in your position all the time and most likely have tools to help you juggle school life. Don't forget to ask questions and for help when you need it. xx
