This is a very powerful technique to strongly bring your awareness to the present moment.

Just Stop! was used widely by enlightened master George Gurdjieff.

Just as you have the impulse to do something, stop. Your cunningness is also one more impulse – one more impulse for your survival. You always think you will survive only if you are cunning and constantly on guard. Now suspend that cunningness. Be innocent and trusting.

Second step, whenever you have an impulse like hunger, anger, thirst or sneezing or any other urge to act, when it is about to happen or when you are about to act, just stop. Move to the space of ‘being’ from the space of ‘doing’.

source: Living Enlightenment