Yoga can be a great way to help deal insomnia, both in the short term and chronic sense. What you want to do is try doing some yoga exercises around 30 minutes before you go to bed. You'll want to do exercises slowly. This will put your mind in the moment of the stretches and you'll eventually stop thinking about things.
Here are some exercises you can try that may help you out.
Sukhasana
All you want to do here is sit on a math with your legs cross. You want the heels of your feet under the other legs thigh. Keep your back erect and straight. Place your hands, palms down, on your knees. You'll want to close your eyes, keep your head up and this should help relax you.
Talasana
This is a really easy exercise. You'll want to stand up as straight as possible. Slowly raise both arms as high as you can in the air. Rise on your toes as your arms go in the air. You're basically trying to reach as high as you can. Hold this position for around 10 seconds. Repeat.
Konasana
This is actually a very common stretch that athletes do. What you do is sit down on a mat and bring the bottoms of your feet together. Pull them in as close to your body as possible. Take your hands, wrap them around the top of the feet and pull yourself forward.
Utkatasana
This is basically a yoga squat. You just want to stick your arms straight out in front of you, keeping them parallel to the ground, than squat. The only thing different is that you want to rise up onto the tiptoes as you go down. As for breathing, breath in when you go up on the tips of your toes.
Upward Dog Forward
This is a pretty simple one. You'll want to lay flat on the floor, with your toes stretched out completely. Push your upper body up with your arms, until they're straight.
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