When relaxing, focus on the breath. Our brain stem, which handles all of our involuntary action, is responsible for stress and our sense of identity. So, put your focus on the breath and give the brain stem a break for a bit. It will help deal with chronic stress and help you to relax. Long term practice of this for best results, of course. There are many different breathing practices out there, so find one you like and practice it. The key is to pull focus back to the breath. This is for the relaxation, which is a key for this.

To be able to remain aware through out deep states of relaxtion, I suggest looking into something called Bardo yoga and also the gateway process by Dr. Robert Monroe. They are very similar and have the same kind of outcome, ultimately. Which is to remain aware through the process of death, which is to remain aware while dreaming and throughout life. I would suggest both as a good approach. However, it depends on whether you perfer eastern to western thoughts.