When The Light Dims, The Darkness Begins
This is how distraction occurs.

When the emptiness of clarity dims, our attention ‘surfs’!

This is from Fearless Simplicity by Tsoknyi Rinpoche:

“I just explained how distraction occurs: the next subject is how to deal with it. Distractions slowly begin when the cognisant quality dims. I mentioned before about the dimming of the light and the beginning of darkness. This awake quality, the cognisant nature, seemingly begins to dim, and together with that is a freezing of the attention towards something. When this occurs to such an extent that the cognisance loses track of being empty, then distraction has begun. But if you are aware of this just as it is about to happen – if you are aware that your attention is about to move into a thought, about to become distracted, and at that moment you re-recognise the empty quality of this awakened state – then there is no distraction. The quality of freedom is re-established.”