About This Answer
Does someone who reached a stage of practice in a past life know it when reborn? Ajahn Dtun says that once they practise again they will know how far they had come. They still have to retread the old ground, but it is easy because the mind already knows the way; the only doubt is at the point where they had stopped.
Asked whether a stream-enterer could be reborn and make no progress in that life because of kamma, he says this is hardly possible. One who has reached the Dhamma only goes forward, like a large ship that has entered a small canal: it cannot turn around and flows on to the great ocean, Nibbāna.
He then speaks of contemplation in daily life. Normally the body is contemplated when the mind is calm, but anything can prompt it: a dead dog or bird by the roadside shows that this body too will decay; at a funeral one reflects on how the person died and that they return to the four elements, as one will oneself. This recollection of death guards against heedlessness.