Apparently this comes from a writing called "On Inner attention (Nepsis)" by St Nektarios de Aegina (a monk from the Greek Orthodox church, who lived about 100 years ago). Not sure how accurate the translation is, the Greek language can be very complex.
Also, it is surprising to find what seems to me a method of insight meditation incorporated into Christian prayer practice.
I am not sure how the above mentioned author was using this approach to insight but some other resources found on youtube suggest that the method is about binding all senses to a sense object (likely conducing to a calm abiding meditation) at the same time with mindfulness of thoughts and emotions.
Attention is the first teacher of truth and consequently absolutely necessary.
Attention rouses the soul to study itself and it's longings, to learn their true character and repulse those that are unholy. Attention is the guardian angel of the intellect, always counseling it to be attentive. Attention awakens the soul, rouses it from sleep ...
Attention examines every thought, every desire, every memory. Thoughts, desires and memories are engendered by various causes, and often appear masked and with splendid garb, in order to deceive the inattentive intellect and enter into the soul and dominate it. Only attention can reveal their hidden form. Often their dissimulation is so perfect that the discernment of their true nature is very difficult and requires the greatest attention.
One must remember the saving words of the Lord: "Be wakeful and pray that ye enter not into temptation".
He who is wakeful does not enter into temptation, because he is vigilant and attentive.