How do you "breathe your troubles away?"I want to know all the information about this.

In the practice of yoga, pranayama is
the ancient art and formal practice of controlling the
breath.

The basic technique includes settling the body and
the mind in a quiet place and in a position of rest (either sitting, lying down, or even
standing).  The idea is to take a full 6-7 seconds to breathe in and a full 6-7 seconds
to breathe out.  During this time, it is recommended that the participant clear his
thoughts by focusing on mentally following the breath to certain areas of the body. 
Spiritually or emotionally speaking, it is the same thing as meditation.  This calming
of the heart, mind, and spirit lowers the heart rate, provides "active rest," and is
said, if practiced with regularity, to provide a host of health
benefits.

Scientifically speaking, this makes sense. 
Consider the body's process of removing waste from the system.  The digestive system is
not doing all the work.  Many people forget that carbon dioxide is also
waste in the human body.  Inhaling deeply increases the flow of
oxygen to all of the organs (including digestive organs) and exhaling "deeply" removes
waste.  Controlled breathing has been linked to increased respiratory and cardiovascular
vitality, decreased nervous activity, and overall improvement in physical and mental
health.

For more detailed information, see either of the
links below.