"In terms of what makes Monadal change possible, we would say it is a culmination of both internal and external factors which ally together to create the necessary incubation for the perceptual shift to occur.” Michael 2009
During the course of our lives there are many transitions, turning points or markers where we cross into new territory. The 7 Internal Monads as discussed in the Michael Teachings are age specific and include birth, the "terrible twos", adolescence, mid-life crisis, life review, the onset of whatever will cause death, and the last breath. Every person engages the 1st (birth), 6th (onset), and 7th (death) in each life, and the remaining (2-5) need be accomplished during each soul level in order for progress to occur. (to the next level). There are also positive and negative poles for each monad and the monads build upon each other.
Birth age 0 - Life + Vitality The taking of the first breath
2nd 2-3 -Solipsism + Identity Differentiation from the mother
3rd 12-30 -Separation +Independence Differentiation from family of origin
4th 35-50 -Acquiescence +Self realization True personality emerges from false
5th 65-75 -Evaluation +Appreciation Life Review
6th variable - Capitulation +Catharsis Onset of whatever will prove fatal
7th variable -Fatalism +Transcendence Begins with the last breath
During these transitions perceptual changes occur within which then allows each person to relate to the external world in a different way based on the new understanding of the Self. And, as Michael has said, there are usually external factors which occur which propel the individual toward internal processing which is the hallmark of each monad.
For more detailed information on the monads, please read my book "Spiritual Turning Points: A Metaphysical Perspective of the Seven Life Transitions c.2011 Available at all major book sellers and online.