References – AN 3.102: Basis 
Readings by Ajahn Pasanno:
The Island by Ajahn Pasanno and Ajahn Amaro, Chapter 13, pp. 230-233:
Suttas: MN 29.7; MN 24.10; AN 3.101; MN 70.13, .22 & .23.
Sutta: AN 3.102: Nimitta.
Sutta: MN 70: Kīṭāgiri Sutta.
Readings from The Island [2025], Session 24
“Could [the principles in AN 3.102] also be related to practicing anāpānāsati?” Answered by Ajahn Pasanno. [Investigation of states] [Right Effort] [Mindfulness of breathing]
Quote: “Dhamma is that which is just right.” — Ajahn Chah. [Ajahn Chah] [Dhamma]
Quote: “Dhamma is neither high nor low, not dark or light, not tall or short. It’s just right.” — Ajahn Kinaree. [Ajahn Kinaree] [Middle Path]
Readings from The Island [2025], Session 24, Excerpt 1
“In practice, how do you know if you are tending towards laziness or restlessness, etc.?” Answered by Ajahn Pasanno and Ajahn Karuṇadhammo. [Investigation of states] // [Concentration] [Direct experience] [Clear comprehension] [Ajahn Sumedho]
Sutta: AN 3.102: “The mind becomes malleable, wieldy, luminous, not brittle...”