Sign up for CNN’s Stress, But Less newsletter. Our six-part mindfulness guide will inform and inspire you to reduce stress while learning how to harness it . CNN  —  Your parents may be right: Get some sleep and you’ll feel better in the morning, according to new research. “Our study suggests that people’s mental health and wellbeing could fluctuate over time of day,” said lead study author Dr. Feifei Bu, principal research fellow in statistics and epidemiology at University College London, in