The book that I have most recommended to friends, family, and clients is The Power Of Now.
To summarise the key themes; the mind is a construct of time - past and future. But all that really is, is now.
Your past is a memory of what once was now, and the future a fiction your create based on what may or may not play out in the now. You are also not your mind. This is why leading expert on happiness Mo Gawdat calls his mind Becky - to disassociate himself from what ruminates within it. The book teaches you to "watch the thinker", your mind, and catch the mind when it rolls off on a stream of (usually damaging) thought. This concept alone is what allowed me to overcome depression many years ago. I would recommend reading this book, not listening to it - as someone that only ever listens to audiobooks - for the true effect. If you open the book and find it to be mumbo jumbo, put it down and come back to it at a later point in time - and please take it's content with a pinch of salt. Like many areas of spirituality and religion, focus on the message rather than the words and tales that are used to depict it - I know this is of benefit to me.