You might like The Happiness Trap by Dr Russ Harris. The start of the book is about how humans have evolved to be SAFE not to be HAPPY. It's our culture that's out of whack not our bodies/minds, but it is good we won't get eaten by bears anymore and we can do more important things than just survive. So some of us with trigger-happy flight/fight responses need to teach our bodies there are no bears. Sometimes you won't be able to help being anxious but you can lessen the impact by not adding what Claire Weekes called the "second fear" - worrying about being anxious. The DARE Response by Barry McDonagh is another good book, and of course Claire Weekes own books.