Here is a book that I have found very helpful. Rick Hanson , a neuropsychologist and meditation teacher, wrote the book "Buddha's Brain" with Richard Mendius, MD. Do not be put off by the title. You do not have to be Buddhist to understand the information and get support by applying the simple exercises in this book.
It is a paperback book, reasonably priced, that I keep near by, to consult every so often when times become disheartening or stressful for me. It is a powerful reminder to me at these times that I have all I need physiologically to recalibrate my nervous system from flight or fight into relaxation. Whether I am caught up in worry and anxiety or intense excitement I am reminded that I am only human and by breathing in and out 5 times in a focused way I can be kind and compassionate to myself. It just takes redirecting my attention and focus. Chapter 5, titled "cooling Fires" gives many effective exercises you can follow and he then gives an explaination of how these exercises impact your nervous sytem and brain chemistry. I was given this book by a dear friend , and I in turn have given this book to other dear friends!