Prana or life energy is required for the proper functioning of our body, for good health and to experience a sense of aliveness. 
In ancient times Yogis knew the connection between the breath and thoughts  and so they developed Pranayama (breath control or breath awareness) exercises in order to ‘manage’ the mind. Managing the mind means you are not a victim to your desires or your thoughts, but you use discernment with whatever thoughts may arise. You are also practicing to live in the Now, harmonious with your life’s purpose and being aligned to your True Being. While breathing evenly and with awareness it is impossible to have negative thoughts or to think excessively. You can watch this yourself when you experience the opposite—for example when you are angry your breathing is totally chaotic. Many people are very busy, stressed, unfocused or confused or in other words they are not in line with their authentic Self. It is a known fact that we don’t breathe properly when we are stressed. As a result it is very difficult to be able to be in touch with true Beingness.
It is not surprising that people who wish to relax start with becoming aware of their breath. Breathing rhythmically is a great beginning towards feeling more centered and relaxed. In balanced aware breathing there is a sense of simply being in our natural state.
Pranayama exercises take it a step further. These exercises use different rhythms in breathing, including breath retention. Breath retention can be after inhaling or after exhaling. They are the pauses between the breath. These pauses are like the zero point zones where we access higher consciousness and where we access realizations and a knowing beyond any doubt.
I personally love to do Pranayama exercises and am happy to share them with others who are sincerely interested in learning them in the Yogic Meditative Healing sessions or workshops.
Even though in the past yogis were very reluctant to teach Pranayama Exercises to students because of their powerful effects and the misuse. We have reached a level of awareness that makes us ready to practice Pranayama Exercises and benefit immensely from them.