I recently picked up a book that I think is going to be a good one. It's called Living Without Worry: How to Replace Anxiety With Peace, by Tim Lane. You might be familiar with Lane through his books, co-written with Paul Tripp, How People Change, and Relationships, a Mess Worth Making.
I'm only into the first part of the book, but I found this passage very good. Lord willing, when I am finished, I will review the book.
The essence of worry is in attempting to find your ultimate hope, comfort, and meaning in something that is temporal and fleeting. It happens when you treat something in creation as a "god" -- so you rely on it, and seek blessings in it. When you do that, you have set yourself up for worry, because nothing in creation lasts and nothing in creation has everything under control (including you!). This world lacks the stability you need in order to be worry free. If you put your hope in things that are unstable, you will be unstable. Your loyalty is divided between something in creation (money is just one example) and God. Something in creation (even a good thing) is usurping the rightful place that only God deserves in your life. Whenever you put your ultimate hope in anything in this world, you will struggle with worry. The more you do this, the more pronounced your struggle will be.There is a little snippet to generate your interest. I'm thinking it will be a good read.