" Another important point is that the more cortisol in an infant’s body, the less the child will sleep, and the less sleep, the more cortisol. In the daytime, the more cortisol, the more fear, the more fear, the more cortisol. Uninterrupted sleep at night and timely naps all reduce cortisol in infants. And remember, lower cortisol also means fewer short-term alarms. It was easy to see that this was a constant problem with Rob. It may have been for you, too. Furthermore, if sleep problems beginning in infancy are not controlled, they may last into adulthood and make a highly sensitive person almost unbearably sensitive. So get your sleep! "

― Elaine N. Aron , The Highly Sensitive Person: How to Thrive When the World Overwhelms You