Henk Barendregt: Reasons for a dark night (pdf).
Abstract Mind is modular, consisting of coordinated units, without central processor. This may be perceived consciously, leading to the experience of change, selflessness, and suffering (the three fundamental characteristics of consciousness). Of these three the first two (change and selflessness) are essential, the third (suffering) is a consequence of craving. Systematic training may lead to (partial or total) letting go, having as consequence diminished suffering, increased flexibility, and more possibilities for inner peace.