One You is a campaign run by Public Health England which offers tips, tools, support and encouragement to help everyone improve both their physical and mental health and reduce their risks of disease/illness in later life.
The website is full of resources to help you assess how healthy your lifestyle is currently and then make the necessary changes, for example to quit smoking, drink less, eat better or move more. In addition, there are lots of resources to help you to reduce stress and anxiety, improve mood and improve sleep.