Answer to Question 1
By learning how to relax the somatic nervous system, Jacobson believed that the sympathetic branch of the autonomic nervous system would follow suit. Indirect evidence for this idea is found in research results showing reduced heart rate and blood pressure when using this procedure (see Bernstein, Carlson, & Schmidt, 2007). Likewise, successful application of his method results in the mind and emotions becoming calm. For example, a recent meta-analytic review (Manzoni, Pagnini, Casetelnuovo, & Molinari, 2008) confirms that relaxation training is especially effective for reducing anxiety. The review found an average effect size in the medium-high range of .57 for relaxation training (i.e., progressive muscle relaxation, applied relaxation, autogenic training, and meditation) with progressive muscle relaxation being one of the most effective strategies. The process requires no exertion of willpower to relax, but rather relaxation happens naturally as a result of tensing and then releasing the contraction of the body's different muscle groups.
Answer to Question 2
When you listen to a guided imagery recording or reading, allow yourself to become fully immersed in the imaginary world. If you have any unwanted thoughts or images, allow them to pass through your consciousness like leaves falling on a stream. There is no need to try to fight them but rather simply refocus on the relaxing images and continue with the process.