Naturally, that awareness cannot be constant. But to be aware that it is not constant, is to be aware of inattention. To be aware of inattention is attention. One cannot reasonably, sanely, say: "I am going to be alert from the moment I wake up until the moment I go to sleep" - one cannot, unless one is neurotic and practises saying: "I am going to be aware, I am going to be aware" - then it becomes words and has no meaning. But if one sees that attention, awareness, cannot be maintained all the time - which is a fact - then inattention, not being attentive, has its value, has its meaning; because in inattention you discover that you are not attentive.
K, Saanen July 1980 Q/A
ca pana, bhikkhave, bhikkhu citte cittanupassi viharati?
Observation of Mind
O monks, how does a monk abide, observing mind within mind? ('mind'
as 'mind' - as it is' - staying with 'what is')