I recommend Yoga as well. I asked (almost) this exact same question to another forum back in January. I got a variety of good recommendations, but the best was definitely Yoga and Meditation, followed by organizational/time-management ideas. Exercise wasn't a problem as I was already exercising hard 4-5 times a week. Sleep wasn't really an issue either, but sleep is basically a prerequisite for any of these ideas. If you aren't getting enough sleep, you won't be able to focus on anything.
Just as a sample, try this:
Find a quiet, clean room with a hard floor that you can still lie down on and be comfortable. It should be softer than a hardwood floor, but harder than a mattress. I used a throw rug on top of a carpet. Get a small blanket or a pillow for your head. I used a $5 fleece blanket from the drugstore.
Lie flat on your back, with your arms slightly away from your body, palms-up. As you relax, your feet should dangle away a little, and your fingers should curl up a bit. Take a deep breath in through your nose by expanding your diaphram. Exhale slowly, and listen to your breath. Continue breathing easily. You should settle into a rhythmic pattern eventually. Keep listening to your breath. Eventually you'll notice that your arms and legs are getting heavy, as the tension drains out of them. Your mouth and eyes and face should relax too. Your mouth will probably hang open. It can take a long time. The first time I did it, it was 20 minutes of lying on my back and breathing before I was really relaxed.
Decide in advance how long you will permit yourself to meditate. I recommend 30-60 minutes. While you are meditating, do not think about anything else at all. If, while you're trying to relax, you begin thinking about your startup, or any other problems, stop and go back to listening to your breath.
The advantage of meditation and Yoga over guns or sports or even martial arts is that you can meditate almost anywhere, and mental discipline is useful for virtually everything.
Just as a sample, try this:
Find a quiet, clean room with a hard floor that you can still lie down on and be comfortable. It should be softer than a hardwood floor, but harder than a mattress. I used a throw rug on top of a carpet. Get a small blanket or a pillow for your head. I used a $5 fleece blanket from the drugstore.
Lie flat on your back, with your arms slightly away from your body, palms-up. As you relax, your feet should dangle away a little, and your fingers should curl up a bit. Take a deep breath in through your nose by expanding your diaphram. Exhale slowly, and listen to your breath. Continue breathing easily. You should settle into a rhythmic pattern eventually. Keep listening to your breath. Eventually you'll notice that your arms and legs are getting heavy, as the tension drains out of them. Your mouth and eyes and face should relax too. Your mouth will probably hang open. It can take a long time. The first time I did it, it was 20 minutes of lying on my back and breathing before I was really relaxed.
Decide in advance how long you will permit yourself to meditate. I recommend 30-60 minutes. While you are meditating, do not think about anything else at all. If, while you're trying to relax, you begin thinking about your startup, or any other problems, stop and go back to listening to your breath.
The advantage of meditation and Yoga over guns or sports or even martial arts is that you can meditate almost anywhere, and mental discipline is useful for virtually everything.