Originally Posted by
SoaringSpirits 
My therapist gave me this tool that kind of switches your brain from the "reptile" portion to the thinking portion; it's used for folks with PTSD. Wherever you are, perform an inventory of what you see, hear, smell and the sensations on your skin. This has really worked well for me.
There is a great book, recomended to me by LTD; it is called What happy people know by Dan Baker. The book deals with many things, and there is a lot in it about the way we think, what happens in our brain, and how we can alter our thoughts. It has been a huge help to me, and it gave me a whole new perspective on life, my behaviour, my thoughts and how much of it depends on me.
I highly recomend it.
IN regards to obsessing the main idea is that it comes from the fear, and that fear comes mostly from the part of our brain that is called a reptile brain (the part of brain that developed first during the evolution and the first part of our brain that develops in the womb) and that is the part of brain where our survival insticts are stored - threre in no room for rational thoughts there, but we have other parts of brain - most importantly neocortex in which our rational thoughts are processed. Dr Baker, based on scientific research, claims that there is a window of 1/4 seconds in which we can chose which train of thought we are going to take, and 1/4 seconds is supposed to be more than enought time for make that decision. IN my mind that translates we always have room to decide what and how we're going to think. ...
BTW book is not too scientific to read at all. It is very interesting, with a lot of real life stories, and quite funny at times too.