Breath and breathing. How does it affect us?

I am curious about breathing. I know that when you breath energy travels through your body. Does this affect the matter and energies around us? What is the spirtual meaning behind breath? What about holding your breath? Is that a negative thing?

 

Actually retention (the act of holding your breath) is very powerful. feel your breath in your Hara (Sacral[2nd] Chakra), hold it there. be filled with healing love and acceptance. While we take in prana as we breath, it is mostly intention and emotion which affect our matter and our radiance. i hope ive been able to help. if there anything else you want to talk about, or anyone else, drop me an IM at goodvibes921 on AIM. be merry :-D

 

How long should I hold by breath, and should I exhail normally or through my mouth? Should I repeat some mantra when I do this? Thanks for the info. It is very interesting to me.