-MN 128"But before long the light and the vision of forms vanish.
We haven’t worked out the pattern of that.”
tañca nimittaṃ nappaṭivijjhāmā”ti.
“Now you should work out the pattern of that.
“Taṃ kho pana vo, anuruddhā, nimittaṃ paṭivijjhitabbaṃ.
Before my awakening—when I was still unawakened but intent on awakening—I too perceived both light and vision of forms. But before long my light and vision of forms vanished. It occurred to me:
'What’s the cause, what’s the reason why my light and vision of forms vanish?’
‘ko nu kho hetu ko paccayo yena me obhāso antaradhāyati dassanañca
It occurred to me:
Tassa mayhaṃ, anuruddhā, etadahosi:
‘Loss of focus arose in me, and because of that my immersion fell away.
‘amanasikāro kho me udapādi, amanasikārādhikaraṇañca pana me samādhi cavi.
Yoniso Manasikara is needed from beginning to end from Right View to Right Concentration
The 5 hindrances pull attention away from good objects (satipathana, one pointedness, single objectness, nimitta) to bad objects (objects of sensual desire, doubt, etc..)