How to Stop Worrying and Start Living, by Dale Carnegie. This book is about exactly what it says, whether you worry a lot or just a little bit this is an excellent book. The thinking and ideas in it are simple but that is what great truths are, obvious once said. There are a lot of ideas on how to frame things or think about things differently where your reaction will be, WHAM, "of course that's how to think about it." Highly highly recommended.