This isn't a revision tips post as by now revision will (hopefully) be well under way as exams are just around the corner... sorry for the reminder. Instead, I wanted to give you my advice on keeping mentally healthy throughout the exam season. The tips could probably also be used at any time of the academic year as it can all be pretty stressful and overwhelming but they will hopefully be particularly useful at the moment.

1. Plan revision. Often people suggest making a revision timetable and whilst this works for some, when I tried it for myself, it put more stress and pressure on me, which just made me want to do less revision not more! Instead I have found it more effective to revise and work when I feel productive (or at least not unproductive!) and keep track of what I've done after. Alternatively, I'll list the topics I need to make reivsion resources for or need to go over and cross them off as I go along rather than dedicating a certain amount of time to each thing. Of course, if you find a revision timetable useful, you're probably better off sticking with that method. 
2. Make sure you leave time to relax. Again, a lot of people suggest taking regular breaks as you're revising or working but I much prefer to work solidly and then have time for myself after I've done everything I want to get done. (Although, breaks are proven to help with concentration and help your eyes if nothing else!) Sometimes this means I do several hours in a block only breaking for food or to use the bathroom but I always try to give myself plenty of time to watch TV, relax in the bath, read a book or do whatever else just to unwind and do something fun afterwards.
3. Get some healthy, easy to grab snacks. I'm sure I'm not alone in that when I'm working I often find myself reaching for snacks to keep me going and often the easiest to grab are not the healthiest which often makes me feel a bit bleurgh afterwards. Instead I like to grab a naked bar, some frozen fruit, some normal fruit, a rice cracker or something like that to nibble on while I work, which stops me from feeling worse afterwards.
4. Have a water bottle handy when you're working. It's great to keep hydrated whilst you're hunched over a pile of notes or revision guides but there's nothing worse than knocking over a glass of juice and smudging your lovely posters or revision cards. A water bottle helps to limit the amount of liquid that could run onto your work should the worst happen.
5. Exercise. I know, I know you've heard it before and it probably doesn't sound any more tempting now but I really do recommend you leave a bit of time to do a workout of some sort. As dull as it sounds, I feel so much better knowing I've taken time to look after my body but equally as important, it's great mentally as I have something else to concentrate on and little chance to think and overthink about the abundance of work waiting for me at home. For this reason, I like to make the effort to go to the gym rather than doing a home workout as I feel like I've gone out specifically to do it and so it needs it's own part of the day, away from education.
6. Get out of the house. Whilst it's important to spend a lot of time working on your subjects and preparing for your exams, it's also important to get out of the house and not just to attend lessons but also to socialise. It's highly likely, and for good reason, that your social life will deteriorate but it doesn't have to drop off the face of the earth. Spending time away from studies with friends and family can help clear your head and give your mind the break it needs before continuing with your work later that day or the next day. 
7. Remember that exams aren't everything. Throughout the majority of our school lives, the importance of exams is drained into us but what often gets forgotten is that exams aren't everything- preparing for and completing an exam to the best of your ability is important yes, but if it doesn't go to plan, there are other ways to get wherever you want to go. It's easier to say than do but bear this in mind and try not to put yourself under a heap of pressure when there are alternative methods.