Dedicate time in your week to see friends:
By setting aside some time in your week to spend time with friends or family, you will see an extreme increase in your mood. I made a pact with myself that Saturday nights no matter how much work I'd have that week, I'd always go out with friends. This ensured for the whole week I'd have something to look forward to. It also ensured I had a life outside of VCE/ QCE where I could do normal stuff. When I saw friends, sometimes I would make it a big thing where we would go into the city and go to a nice restaurant or we'd go to a party but other nights we would just go to someone's house and make pizza or watch a movie. Either way, any kind of human interaction in an environment that wasn't in school really boosted my mood.
Continue with your extra-curricular activities:
I know many people stop playing sports or doing all their other extra-curricular activities to focus on VCE/ QCE. However, by stopping all these activities that give you enjoyment, you will really dampen your mood. You need to continue doing the things you love in order to keep you going. If your spending your whole year simply doing schoolwork and nothing else, you will feel like you're a prisoner.
Also, I often found by having a scheduled activity every week at a certain time, it would give me some structure to my day which would ensure when I was studying I'd work harder. Often on the days when I'd have nothing on in the afternoon, I'd spend a long time doing homework that I could've done in 30 minutes simply because I'd feel like I had no pressure to get it done quickly. Studies show that people study more efficiently when they are busy and have to work quickly.