Complex sentence: The smoothness and duration of the shift into each phase is determined by psychological self-knowledge, which he believes will play a vital role in helping untrained family caregivers better understand themselves and their own reactions to the unique and challenging pressures that domestic caregiving creates.
Split into simpler sentences: The smoothness and duration if the shift into each phase is determined by psychological self-knowledge. He believes that such self-knowledge will play a vital role in helping untrained family caregivers better understand themselves and their own reactions to the unique and challenging pressures that domestic caregiving creates.