When doing aikido, practise expanding your peripheral vision. By taking in your surroundings you become more aware. You learn to notice each movement your opponent makes.
If you focus too juch on one point, you will be easier to distract. Your ki will be easier to take off balance.
Learning to gaze works hand in hand with increasing your field of vision. You give your eyes something to look at, but not truly focus on. Once your eyes are steady you will be able to take in your surroundings via your peripheral.
The image above shows the way we practised using our peripheral vision. At first we kept mi between ourselves while walking up and down the mat with our opponent. Having our hands up like the above picture gave us something to focus our peripheral vision on.
Next we would hone in our focus onto one point of our opponent and see how tunnel vision can effect our pursuit of the other person. It was a lot easier to get off balance without the opponent even trying to distract you. Even getting your feeling was difficult, I nearly tripped over my own feet in this variant of the activity.
Thirdly we were to practise keeping our mi by simply having our hands out as if we were holding a blade. The aikido stance. Ready to attack. Focusing on the peripheral definitely made this easier to do. My partner was good to practise with as he would change the pace he was moving without warning, ensuring I was correctly adjusting my speed to ensure our distance was maintained.