How can I stop thinking and shut my brain off?

Sometimes it's difficult to avoid overthinking.A good tip is to always remember that these thoughts are your own,you are the one who has the control over them and nobody else.Also,doing some creative activities,that keep your mind focused,such as drawing,are really helpfull.

You could try deep breathing exercises to calm you? Breathe in for 4, hold the breath for 7 then breath out for 8 :)

Learn to practice meditation (Headspace makes it really easy, OMG I can meditate too), get out for a walk / run, write your thoughts down, ... Don't try to push them away as it'll make it harder for you. Embrace your thoughts, understand them, and then you'll be able to let them go :)

Mindfulness techniques like listening to guided meditation work at times, and distracting myself, be it tasks that have to be done, random busywork, or passing time doing something like watching a movie or listening to music. Basically, something to occupy the mind. Therapy and medication for me, the latter being the most effective.

Physical activities take your energy off your mind & put it on your body. Plus it helps get rid of that nervous energy. Or even just thinking about the physical world around you-what you see through your senses at that moment-helps you get your mind off your past & future worries

I usually go swimming. It makes me feel free. Keeping busy is useful to stop thinking, even hanging out with a friend and laugh may help

Oh dear why would you do such a thing! Too many people do the complete opposite. If you are going into overdrive unwillingly, organizing your thoughts is one of the best ways to "make the voices stop". I personally begin writing the subject of my thoughts down on paper in random places (use a blank paper). Then i link them together in ways that one is related with the other. For example: I am down about my grades but its because i procrastinate. I procrastinate by playing games. I play because im not happy. Etc. Eventually you will find a pattern and an order in your thoughts. Then you can start handling them individually and make progress ;)

Technically you cant shut your brain off we are not computer so we don't have any switch to turn it of when you brain shuts down it means you are a zombie LOL . the only thing humans are different from other animals we have a attitude and a behavior and your brains controls it and if you think you dont have attitude or a behavior you are nothing but a chimpanzee :P

Do things that are relaxing for you.Watch some tv or listen to music.Those two can easily take your mind off.

I advice you to listen to some good music. It has always got me through a lot of hard times, so this is great.