What is more challenging is going the other direction. How do we actually take those negative thoughts and shift them to the positive, or just observe and be with them?
As the days go by, I find meditation to be perhaps the most significant tool I have in my toolchest. After 4 years of practicing (wow, can that be) I am recently aware of the moments when I can just observe and be with whatever is coming up.
The book that I still credit with starting my meditation journey is Living In the Light: A Guide to Personal and Planetary Transformation by Shakti Gawain. A beautiful book with great meditation/breathing exercises at the end of each chapter. A wonderful addition to any personal growth library. But don't leave it on the shelf!