If you have carried something heavy by yourself, whether It is a piece of furniture, bags of food, pail of water or others, what is your mind thinking at that point of time?
Most of us will only be concerned about the weight, the heaviness of the object or feeling the muscle pain. During the carry process, you hardly will entertain thoughts like admiring the beautiful surrounding, thinking of what clothes to wear later or what you are going to eat for lunch or even whistling to enjoy yourself. All these become much lesser in priority during the process.
This is focused attention on one particular thing. It is hypnosis.